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	$89.39	13.711%	$101.6463	$101.65	$101.65	$101.60
Purchase #2	$166.38	11.116%	$184.8748	$184.87	$184.85	$184.90
Purchase #3	$21.69	4.576%	$22.6825	$22.68	$22.70	$22.70
Purchase #4	$107.77	3.146%	$111.1604	$111.16	$111.15	$111.20
Purchase #5	$6.78	6.139%	$7.1962	$7.20	$7.20	$7.20
Purchase #6	$38.83	7.813%	$41.8638	$41.86	$41.85	$41.90
Purchase #7	$55.56	11.625%	$62.0189	$62.02	$62.00	$62.00
7 purchase totals =	$486.40		$531.4429	$531.44	$531.40	$531.50