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	$59.29	6.146%	$62.934	$62.93	$62.95	$62.90
Purchase #2	$76.80	10.676%	$84.9992	$85.00	$85.00	$85.00
Purchase #3	$152.67	13.756%	$173.6713	$173.67	$173.65	$173.70
Purchase #4	$88.61	7.344%	$95.1175	$95.12	$95.10	$95.10
Purchase #5	$250.34	10.475%	$276.5631	$276.56	$276.55	$276.60
Purchase #6	$139.88	9.691%	$153.4358	$153.44	$153.45	$153.40
Purchase #7	$88.75	13.604%	$100.8236	$100.82	$100.80	$100.80
7 purchase totals =	$856.34		$947.5445	$947.54	$947.50	$947.50