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	$88.62	8.250%	$95.9312	$95.93	$95.95	$95.90
Purchase #2	$89.75	12.453%	$100.9266	$100.93	$100.95	$100.90
Purchase #3	$246.96	11.861%	$276.2519	$276.25	$276.25	$276.30
Purchase #4	$122.80	7.603%	$132.1365	$132.14	$132.15	$132.10
Purchase #5	$68.93	13.539%	$78.2624	$78.26	$78.25	$78.30
Purchase #6	$70.73	8.294%	$76.5963	$76.60	$76.60	$76.60
Purchase #7	$171.60	11.767%	$191.7922	$191.79	$191.80	$191.80
7 purchase totals =	$859.39		$951.8971	$951.90	$951.95	$951.90