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	$106.31	4.838%	$111.4533	$111.45	$111.45	$111.50
Purchase #2	$190.90	12.238%	$214.2623	$214.26	$214.25	$214.30
Purchase #3	$230.97	9.493%	$252.896	$252.90	$252.90	$252.90
Purchase #4	$225.31	11.554%	$251.3423	$251.34	$251.35	$251.30
Purchase #5	$136.29	3.256%	$140.7276	$140.73	$140.75	$140.70
Purchase #6	$216.29	3.501%	$223.8623	$223.86	$223.85	$223.90
Purchase #7	$110.52	11.804%	$123.5658	$123.57	$123.55	$123.60
7 purchase totals =	$1,216.59		$1,318.1096	$1,318.11	$1,318.10	$1,318.20