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	$163.60	11.539%	$182.4778	$182.48	$182.50	$182.50
Purchase #2	$30.38	10.189%	$33.4754	$33.48	$33.50	$33.50
Purchase #3	$78.65	10.269%	$86.7266	$86.73	$86.75	$86.70
Purchase #4	$126.81	3.467%	$131.2065	$131.21	$131.20	$131.20
Purchase #5	$49.82	5.590%	$52.6049	$52.60	$52.60	$52.60
Purchase #6	$189.51	8.485%	$205.5899	$205.59	$205.60	$205.60
Purchase #7	$110.51	7.113%	$118.3706	$118.37	$118.35	$118.40
7 purchase totals =	$749.28		$810.4517	$810.46	$810.50	$810.50