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	$32.71	9.194%	$35.7174	$35.72	$35.70	$35.70
Purchase #2	$182.31	13.301%	$206.5591	$206.56	$206.55	$206.60
Purchase #3	$172.91	10.291%	$190.7042	$190.70	$190.70	$190.70
Purchase #4	$54.75	6.865%	$58.5086	$58.51	$58.50	$58.50
Purchase #5	$222.84	6.161%	$236.5692	$236.57	$236.55	$236.60
Purchase #6	$73.98	4.733%	$77.4815	$77.48	$77.50	$77.50
Purchase #7	$95.60	5.504%	$100.8618	$100.86	$100.85	$100.90
7 purchase totals =	$835.10		$906.4018	$906.40	$906.35	$906.50