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	$222.31	5.133%	$233.7212	$233.72	$233.70	$233.70
Purchase #2	$173.80	12.857%	$196.1455	$196.15	$196.15	$196.10
Purchase #3	$18.51	13.231%	$20.9591	$20.96	$20.95	$21.00
Purchase #4	$242.27	12.596%	$272.7863	$272.79	$272.80	$272.80
Purchase #5	$62.92	10.179%	$69.3246	$69.32	$69.30	$69.30
Purchase #6	$7.34	10.488%	$8.1098	$8.11	$8.10	$8.10
Purchase #7	$134.37	12.842%	$151.6258	$151.63	$151.65	$151.60
7 purchase totals =	$861.52		$952.6723	$952.68	$952.65	$952.60