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	$37.76	13.680%	$42.9256	$42.93	$42.95	$42.90
Purchase #2	$9.54	11.184%	$10.607	$10.61	$10.60	$10.60
Purchase #3	$178.95	12.531%	$201.3742	$201.37	$201.35	$201.40
Purchase #4	$56.53	8.760%	$61.482	$61.48	$61.50	$61.50
Purchase #5	$216.83	7.235%	$232.5177	$232.52	$232.50	$232.50
Purchase #6	$206.87	7.413%	$222.2053	$222.21	$222.20	$222.20
Purchase #7	$98.73	6.641%	$105.2867	$105.29	$105.30	$105.30
7 purchase totals =	$805.21		$876.3985	$876.41	$876.40	$876.40