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	$218.57	11.646%	$244.0247	$244.02	$244.00	$244.00
Purchase #2	$249.51	10.534%	$275.7934	$275.79	$275.80	$275.80
Purchase #3	$138.39	4.362%	$144.4266	$144.43	$144.45	$144.40
Purchase #4	$140.44	8.313%	$152.1148	$152.11	$152.10	$152.10
Purchase #5	$54.30	11.456%	$60.5206	$60.52	$60.50	$60.50
Purchase #6	$37.78	7.488%	$40.609	$40.61	$40.60	$40.60
Purchase #7	$110.43	9.856%	$121.314	$121.31	$121.30	$121.30
7 purchase totals =	$949.42		$1,038.8031	$1,038.79	$1,038.75	$1,038.70