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	$232.80	7.600%	$250.4928	$250.49	$250.50	$250.50
Purchase #2	$59.46	5.244%	$62.5781	$62.58	$62.60	$62.60
Purchase #3	$137.89	13.810%	$156.9326	$156.93	$156.95	$156.90
Purchase #4	$83.55	13.755%	$95.0423	$95.04	$95.05	$95.00
Purchase #5	$180.87	3.561%	$187.3108	$187.31	$187.30	$187.30
Purchase #6	$42.47	4.743%	$44.4844	$44.48	$44.50	$44.50
Purchase #7	$216.86	4.213%	$225.9963	$226.00	$226.00	$226.00
7 purchase totals =	$953.90		$1,022.8373	$1,022.83	$1,022.90	$1,022.80