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	$95.43	10.153%	$105.119	$105.12	$105.10	$105.10
Purchase #2	$139.37	7.547%	$149.8883	$149.89	$149.90	$149.90
Purchase #3	$53.81	8.478%	$58.372	$58.37	$58.35	$58.40
Purchase #4	$148.91	11.406%	$165.8947	$165.89	$165.90	$165.90
Purchase #5	$33.53	8.529%	$36.3898	$36.39	$36.40	$36.40
Purchase #6	$176.96	10.370%	$195.3108	$195.31	$195.30	$195.30
Purchase #7	$90.96	9.137%	$99.271	$99.27	$99.25	$99.30
7 purchase totals =	$738.97		$810.2456	$810.24	$810.20	$810.30