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	$149.47	6.184%	$158.7132	$158.71	$158.70	$158.70
Purchase #2	$214.73	6.201%	$228.0454	$228.05	$228.05	$228.00
Purchase #3	$243.86	13.476%	$276.7226	$276.72	$276.70	$276.70
Purchase #4	$36.25	3.397%	$37.4814	$37.48	$37.50	$37.50
Purchase #5	$233.58	11.761%	$261.0513	$261.05	$261.05	$261.10
Purchase #6	$244.40	11.418%	$272.3056	$272.31	$272.30	$272.30
Purchase #7	$50.55	7.256%	$54.2179	$54.22	$54.20	$54.20
7 purchase totals =	$1,172.84		$1,288.5374	$1,288.54	$1,288.50	$1,288.50