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	$33.75	5.136%	$35.4834	$35.48	$35.50	$35.50
Purchase #2	$137.74	3.496%	$142.5554	$142.56	$142.55	$142.60
Purchase #3	$33.77	3.117%	$34.8226	$34.82	$34.80	$34.80
Purchase #4	$53.72	11.400%	$59.8441	$59.84	$59.85	$59.80
Purchase #5	$161.29	13.214%	$182.6029	$182.60	$182.60	$182.60
Purchase #6	$78.76	9.168%	$85.9807	$85.98	$86.00	$86.00
Purchase #7	$146.40	10.500%	$161.772	$161.77	$161.75	$161.80
7 purchase totals =	$645.43		$703.0611	$703.05	$703.05	$703.10