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	$222.75	4.495%	$232.7626	$232.76	$232.75	$232.80
Purchase #2	$85.78	8.256%	$92.862	$92.86	$92.85	$92.90
Purchase #3	$170.31	6.738%	$181.7855	$181.79	$181.80	$181.80
Purchase #4	$177.52	10.490%	$196.1418	$196.14	$196.15	$196.10
Purchase #5	$18.47	10.697%	$20.4457	$20.45	$20.45	$20.40
Purchase #6	$144.33	10.428%	$159.3807	$159.38	$159.40	$159.40
Purchase #7	$234.25	4.546%	$244.899	$244.90	$244.90	$244.90
7 purchase totals =	$1,053.41		$1,128.2773	$1,128.28	$1,128.30	$1,128.30