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	$210.95	11.485%	$235.1776	$235.18	$235.20	$235.20
Purchase #2	$166.75	7.222%	$178.7927	$178.79	$178.80	$178.80
Purchase #3	$85.70	5.510%	$90.4221	$90.42	$90.40	$90.40
Purchase #4	$69.52	7.648%	$74.8369	$74.84	$74.85	$74.80
Purchase #5	$75.91	10.505%	$83.8843	$83.88	$83.90	$83.90
Purchase #6	$219.32	9.728%	$240.6554	$240.66	$240.65	$240.70
Purchase #7	$174.50	9.754%	$191.5207	$191.52	$191.50	$191.50
7 purchase totals =	$1,002.65		$1,095.2897	$1,095.29	$1,095.30	$1,095.30