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	$124.54	7.495%	$133.8743	$133.87	$133.85	$133.90
Purchase #2	$81.60	9.499%	$89.3512	$89.35	$89.35	$89.40
Purchase #3	$44.90	11.658%	$50.1344	$50.13	$50.15	$50.10
Purchase #4	$39.33	13.717%	$44.7249	$44.72	$44.70	$44.70
Purchase #5	$38.79	3.596%	$40.1849	$40.18	$40.20	$40.20
Purchase #6	$132.49	13.142%	$149.9018	$149.90	$149.90	$149.90
Purchase #7	$23.52	3.849%	$24.4253	$24.43	$24.45	$24.40
7 purchase totals =	$485.17		$532.5968	$532.58	$532.60	$532.60