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	$133.73	13.708%	$152.0617	$152.06	$152.05	$152.10
Purchase #2	$116.37	7.775%	$125.4178	$125.42	$125.40	$125.40
Purchase #3	$53.31	12.299%	$59.8666	$59.87	$59.85	$59.90
Purchase #4	$49.27	9.797%	$54.097	$54.10	$54.10	$54.10
Purchase #5	$168.64	9.408%	$184.5057	$184.51	$184.50	$184.50
Purchase #6	$184.71	9.204%	$201.7107	$201.71	$201.70	$201.70
Purchase #7	$40.58	5.684%	$42.8866	$42.89	$42.90	$42.90
7 purchase totals =	$746.61		$820.5461	$820.56	$820.50	$820.60