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	$102.39	10.144%	$112.7764	$112.78	$112.80	$112.80
Purchase #2	$244.44	3.593%	$253.2227	$253.22	$253.20	$253.20
Purchase #3	$230.57	10.676%	$255.1857	$255.19	$255.20	$255.20
Purchase #4	$184.74	6.565%	$196.8682	$196.87	$196.85	$196.90
Purchase #5	$176.58	8.788%	$192.0979	$192.10	$192.10	$192.10
Purchase #6	$53.59	11.863%	$59.9474	$59.95	$59.95	$59.90
Purchase #7	$166.63	10.489%	$184.1078	$184.11	$184.10	$184.10
7 purchase totals =	$1,158.94		$1,254.2061	$1,254.22	$1,254.20	$1,254.20