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	$132.64	11.840%	$148.3446	$148.34	$148.35	$148.30
Purchase #2	$224.27	4.411%	$234.1625	$234.16	$234.15	$234.20
Purchase #3	$20.48	3.364%	$21.1689	$21.17	$21.15	$21.20
Purchase #4	$100.93	9.363%	$110.3801	$110.38	$110.40	$110.40
Purchase #5	$125.40	9.265%	$137.0183	$137.02	$137.00	$137.00
Purchase #6	$209.54	9.435%	$229.3101	$229.31	$229.30	$229.30
Purchase #7	$108.98	12.414%	$122.5088	$122.51	$122.50	$122.50
7 purchase totals =	$922.24		$1,002.8933	$1,002.89	$1,002.85	$1,002.90