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	$149.86	12.501%	$168.594	$168.59	$168.60	$168.60
Purchase #2	$48.61	7.370%	$52.1926	$52.19	$52.20	$52.20
Purchase #3	$222.47	5.757%	$235.2776	$235.28	$235.30	$235.30
Purchase #4	$36.25	8.211%	$39.2265	$39.23	$39.25	$39.20
Purchase #5	$243.95	9.638%	$267.4619	$267.46	$267.45	$267.50
Purchase #6	$198.84	6.865%	$212.4904	$212.49	$212.50	$212.50
Purchase #7	$59.52	9.470%	$65.1565	$65.16	$65.15	$65.20
7 purchase totals =	$959.50		$1,040.3995	$1,040.40	$1,040.45	$1,040.50