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	$228.95	10.577%	$253.166	$253.17	$253.15	$253.20
Purchase #2	$191.59	4.778%	$200.7442	$200.74	$200.75	$200.70
Purchase #3	$161.37	5.235%	$169.8177	$169.82	$169.80	$169.80
Purchase #4	$85.95	11.612%	$95.9305	$95.93	$95.95	$95.90
Purchase #5	$81.50	11.740%	$91.0681	$91.07	$91.05	$91.10
Purchase #6	$118.51	12.131%	$132.8864	$132.89	$132.90	$132.90
Purchase #7	$154.96	6.853%	$165.5794	$165.58	$165.60	$165.60
7 purchase totals =	$1,022.83		$1,109.1923	$1,109.20	$1,109.20	$1,109.20