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	$235.44	7.702%	$253.5736	$253.57	$253.55	$253.60
Purchase #2	$93.49	7.102%	$100.1297	$100.13	$100.15	$100.10
Purchase #3	$195.60	5.632%	$206.6162	$206.62	$206.60	$206.60
Purchase #4	$11.67	3.593%	$12.0893	$12.09	$12.10	$12.10
Purchase #5	$71.26	9.626%	$78.1195	$78.12	$78.10	$78.10
Purchase #6	$72.48	11.539%	$80.8435	$80.84	$80.85	$80.80
Purchase #7	$66.33	6.263%	$70.4842	$70.48	$70.50	$70.50
7 purchase totals =	$746.27		$801.8560	$801.85	$801.85	$801.80