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	$165.71	11.825%	$185.3052	$185.31	$185.30	$185.30
Purchase #2	$99.77	13.604%	$113.3427	$113.34	$113.35	$113.30
Purchase #3	$6.73	5.602%	$7.107	$7.11	$7.10	$7.10
Purchase #4	$127.66	7.606%	$137.3698	$137.37	$137.35	$137.40
Purchase #5	$89.90	6.315%	$95.5772	$95.58	$95.60	$95.60
Purchase #6	$122.43	9.840%	$134.4771	$134.48	$134.50	$134.50
Purchase #7	$79.42	11.606%	$88.6375	$88.64	$88.65	$88.60
7 purchase totals =	$691.62		$761.8165	$761.83	$761.85	$761.80