Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$154.53	12.763%	$174.2527	$174.25	$174.25	$174.30
Purchase #2	$204.55	5.849%	$216.5141	$216.51	$216.50	$216.50
Purchase #3	$169.74	7.158%	$181.89	$181.89	$181.90	$181.90
Purchase #4	$240.83	11.611%	$268.7928	$268.79	$268.80	$268.80
Purchase #5	$88.29	7.356%	$94.7846	$94.78	$94.80	$94.80
Purchase #6	$95.47	12.474%	$107.3789	$107.38	$107.40	$107.40
Purchase #7	$95.35	5.850%	$100.928	$100.93	$100.95	$100.90
7 purchase totals =	$1,048.76		$1,144.5411	$1,144.53	$1,144.60	$1,144.60