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	$63.25	3.355%	$65.372	$65.37	$65.35	$65.40
Purchase #2	$86.76	7.775%	$93.5056	$93.51	$93.50	$93.50
Purchase #3	$188.33	10.755%	$208.5849	$208.58	$208.60	$208.60
Purchase #4	$10.88	13.805%	$12.382	$12.38	$12.40	$12.40
Purchase #5	$196.72	6.590%	$209.6838	$209.68	$209.70	$209.70
Purchase #6	$83.84	7.837%	$90.4105	$90.41	$90.40	$90.40
Purchase #7	$109.25	13.259%	$123.7355	$123.74	$123.75	$123.70
7 purchase totals =	$739.03		$803.6743	$803.67	$803.70	$803.70