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	$242.97	4.429%	$253.7311	$253.73	$253.75	$253.70
Purchase #2	$232.29	10.251%	$256.102	$256.10	$256.10	$256.10
Purchase #3	$118.49	8.827%	$128.9491	$128.95	$128.95	$128.90
Purchase #4	$113.71	3.390%	$117.5648	$117.56	$117.55	$117.60
Purchase #5	$221.86	5.374%	$233.7828	$233.78	$233.80	$233.80
Purchase #6	$56.48	5.364%	$59.5096	$59.51	$59.50	$59.50
Purchase #7	$219.80	8.551%	$238.5951	$238.60	$238.60	$238.60
7 purchase totals =	$1,205.60		$1,288.2345	$1,288.23	$1,288.25	$1,288.20