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	$243.69	7.563%	$262.1203	$262.12	$262.10	$262.10
Purchase #2	$81.56	11.262%	$90.7453	$90.75	$90.75	$90.70
Purchase #3	$230.98	10.273%	$254.7086	$254.71	$254.70	$254.70
Purchase #4	$14.32	3.211%	$14.7798	$14.78	$14.80	$14.80
Purchase #5	$53.63	10.250%	$59.1271	$59.13	$59.15	$59.10
Purchase #6	$61.82	7.414%	$66.4033	$66.40	$66.40	$66.40
Purchase #7	$72.95	8.113%	$78.8684	$78.87	$78.85	$78.90
7 purchase totals =	$758.95		$826.7528	$826.76	$826.75	$826.70