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	$82.62	9.725%	$90.6548	$90.65	$90.65	$90.70
Purchase #2	$168.89	10.824%	$187.1707	$187.17	$187.15	$187.20
Purchase #3	$233.67	12.524%	$262.9348	$262.93	$262.95	$262.90
Purchase #4	$236.51	10.433%	$261.1851	$261.19	$261.20	$261.20
Purchase #5	$106.82	9.419%	$116.8814	$116.88	$116.90	$116.90
Purchase #6	$11.94	7.185%	$12.7979	$12.80	$12.80	$12.80
Purchase #7	$49.58	7.832%	$53.4631	$53.46	$53.45	$53.50
7 purchase totals =	$890.03		$985.0878	$985.08	$985.10	$985.20