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	$182.56	12.464%	$205.3143	$205.31	$205.30	$205.30
Purchase #2	$131.51	7.437%	$141.2904	$141.29	$141.30	$141.30
Purchase #3	$54.64	3.588%	$56.6005	$56.60	$56.60	$56.60
Purchase #4	$55.43	7.354%	$59.5063	$59.51	$59.50	$59.50
Purchase #5	$154.84	13.373%	$175.5468	$175.55	$175.55	$175.50
Purchase #6	$120.38	4.802%	$126.1606	$126.16	$126.15	$126.20
Purchase #7	$100.83	10.408%	$111.3244	$111.32	$111.30	$111.30
7 purchase totals =	$800.19		$875.7433	$875.74	$875.70	$875.70