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	$53.44	4.662%	$55.9314	$55.93	$55.95	$55.90
Purchase #2	$37.88	4.269%	$39.4971	$39.50	$39.50	$39.50
Purchase #3	$48.61	11.497%	$54.1987	$54.20	$54.20	$54.20
Purchase #4	$39.31	13.581%	$44.6487	$44.65	$44.65	$44.60
Purchase #5	$199.98	11.288%	$222.5537	$222.55	$222.55	$222.60
Purchase #6	$55.98	8.778%	$60.8939	$60.89	$60.90	$60.90
Purchase #7	$135.68	12.345%	$152.4297	$152.43	$152.45	$152.40
7 purchase totals =	$570.88		$630.1532	$630.15	$630.20	$630.10