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	$150.79	7.280%	$161.7675	$161.77	$161.75	$161.80
Purchase #2	$32.55	8.840%	$35.4274	$35.43	$35.45	$35.40
Purchase #3	$148.66	13.372%	$168.5388	$168.54	$168.55	$168.50
Purchase #4	$50.99	6.180%	$54.1412	$54.14	$54.15	$54.10
Purchase #5	$204.96	8.255%	$221.8794	$221.88	$221.90	$221.90
Purchase #6	$100.72	10.313%	$111.1073	$111.11	$111.10	$111.10
Purchase #7	$231.49	5.482%	$244.1803	$244.18	$244.20	$244.20
7 purchase totals =	$920.16		$997.0419	$997.05	$997.10	$997.00