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	$29.61	4.736%	$31.0123	$31.01	$31.00	$31.00
Purchase #2	$70.40	11.172%	$78.2651	$78.27	$78.25	$78.30
Purchase #3	$76.55	11.864%	$85.6319	$85.63	$85.65	$85.60
Purchase #4	$85.37	6.647%	$91.0445	$91.04	$91.05	$91.00
Purchase #5	$248.31	4.119%	$258.5379	$258.54	$258.55	$258.50
Purchase #6	$32.36	11.271%	$36.0073	$36.01	$36.00	$36.00
Purchase #7	$218.97	4.357%	$228.5105	$228.51	$228.50	$228.50
7 purchase totals =	$761.57		$809.0095	$809.01	$809.00	$808.90