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	$247.50	3.312%	$255.6972	$255.70	$255.70	$255.70
Purchase #2	$235.26	5.573%	$248.371	$248.37	$248.35	$248.40
Purchase #3	$50.73	10.102%	$55.8547	$55.85	$55.85	$55.90
Purchase #4	$50.77	11.395%	$56.5552	$56.56	$56.55	$56.60
Purchase #5	$59.69	8.252%	$64.6156	$64.62	$64.60	$64.60
Purchase #6	$60.30	8.638%	$65.5087	$65.51	$65.50	$65.50
Purchase #7	$167.86	11.488%	$187.1438	$187.14	$187.15	$187.10
7 purchase totals =	$872.11		$933.7462	$933.75	$933.70	$933.80