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	$89.70	4.471%	$93.7105	$93.71	$93.70	$93.70
Purchase #2	$192.67	11.359%	$214.5554	$214.56	$214.55	$214.60
Purchase #3	$69.66	13.102%	$78.7869	$78.79	$78.80	$78.80
Purchase #4	$105.25	8.185%	$113.8647	$113.86	$113.85	$113.90
Purchase #5	$203.79	6.177%	$216.3781	$216.38	$216.40	$216.40
Purchase #6	$225.35	13.245%	$255.1976	$255.20	$255.20	$255.20
Purchase #7	$54.96	12.562%	$61.8641	$61.86	$61.85	$61.90
7 purchase totals =	$941.38		$1,034.3573	$1,034.36	$1,034.35	$1,034.50