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	$243.50	4.505%	$254.4697	$254.47	$254.45	$254.50
Purchase #2	$224.59	13.171%	$254.1707	$254.17	$254.15	$254.20
Purchase #3	$23.39	3.191%	$24.1364	$24.14	$24.15	$24.10
Purchase #4	$156.36	3.189%	$161.3463	$161.35	$161.35	$161.30
Purchase #5	$57.61	7.103%	$61.702	$61.70	$61.70	$61.70
Purchase #6	$216.45	6.119%	$229.6946	$229.69	$229.70	$229.70
Purchase #7	$98.64	7.319%	$105.8595	$105.86	$105.85	$105.90
7 purchase totals =	$1,020.54		$1,091.3792	$1,091.38	$1,091.35	$1,091.40