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	$210.88	10.618%	$233.2712	$233.27	$233.25	$233.30
Purchase #2	$38.71	8.149%	$41.8645	$41.86	$41.85	$41.90
Purchase #3	$53.78	12.149%	$60.3137	$60.31	$60.30	$60.30
Purchase #4	$46.72	11.648%	$52.1619	$52.16	$52.15	$52.20
Purchase #5	$246.29	3.468%	$254.8313	$254.83	$254.85	$254.80
Purchase #6	$243.73	13.707%	$277.1381	$277.14	$277.15	$277.10
Purchase #7	$190.75	9.727%	$209.3043	$209.30	$209.30	$209.30
7 purchase totals =	$1,030.86		$1,128.8850	$1,128.87	$1,128.85	$1,128.90