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	$84.52	8.718%	$91.8885	$91.89	$91.90	$91.90
Purchase #2	$103.35	7.442%	$111.0413	$111.04	$111.05	$111.00
Purchase #3	$172.42	3.866%	$179.0858	$179.09	$179.10	$179.10
Purchase #4	$216.25	9.111%	$235.9525	$235.95	$235.95	$236.00
Purchase #5	$225.74	7.208%	$242.0113	$242.01	$242.00	$242.00
Purchase #6	$118.38	10.230%	$130.4903	$130.49	$130.50	$130.50
Purchase #7	$11.77	10.717%	$13.0314	$13.03	$13.05	$13.00
7 purchase totals =	$932.43		$1,003.5011	$1,003.50	$1,003.55	$1,003.50