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	$103.54	6.327%	$110.091	$110.09	$110.10	$110.10
Purchase #2	$51.25	9.226%	$55.9783	$55.98	$56.00	$56.00
Purchase #3	$228.50	7.715%	$246.1288	$246.13	$246.15	$246.10
Purchase #4	$65.70	9.562%	$71.9822	$71.98	$72.00	$72.00
Purchase #5	$136.59	11.219%	$151.914	$151.91	$151.90	$151.90
Purchase #6	$182.30	4.369%	$190.2647	$190.26	$190.25	$190.30
Purchase #7	$241.57	13.455%	$274.0732	$274.07	$274.05	$274.10
7 purchase totals =	$1,009.45		$1,100.4322	$1,100.42	$1,100.45	$1,100.50