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	$165.84	4.464%	$173.2431	$173.24	$173.25	$173.20
Purchase #2	$105.93	5.600%	$111.8621	$111.86	$111.85	$111.90
Purchase #3	$29.63	8.403%	$32.1198	$32.12	$32.10	$32.10
Purchase #4	$198.55	12.257%	$222.8863	$222.89	$222.90	$222.90
Purchase #5	$74.87	4.194%	$78.01	$78.01	$78.00	$78.00
Purchase #6	$55.95	10.180%	$61.6457	$61.65	$61.65	$61.60
Purchase #7	$54.42	7.628%	$58.5712	$58.57	$58.55	$58.60
7 purchase totals =	$685.19		$738.3382	$738.34	$738.30	$738.30