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	$247.37	6.103%	$262.467	$262.47	$262.45	$262.50
Purchase #2	$218.48	11.557%	$243.7297	$243.73	$243.75	$243.70
Purchase #3	$51.78	11.720%	$57.8486	$57.85	$57.85	$57.80
Purchase #4	$39.50	12.217%	$44.3257	$44.33	$44.35	$44.30
Purchase #5	$127.56	8.335%	$138.1921	$138.19	$138.20	$138.20
Purchase #6	$233.39	9.418%	$255.3707	$255.37	$255.35	$255.40
Purchase #7	$209.90	7.325%	$225.2752	$225.28	$225.30	$225.30
7 purchase totals =	$1,127.98		$1,227.2090	$1,227.22	$1,227.25	$1,227.20