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	$190.31	7.314%	$204.2293	$204.23	$204.25	$204.20
Purchase #2	$42.93	4.274%	$44.7648	$44.76	$44.75	$44.80
Purchase #3	$217.45	3.572%	$225.2173	$225.22	$225.20	$225.20
Purchase #4	$26.47	4.491%	$27.6588	$27.66	$27.65	$27.70
Purchase #5	$233.71	9.760%	$256.5201	$256.52	$256.50	$256.50
Purchase #6	$73.56	13.320%	$83.3582	$83.36	$83.35	$83.40
Purchase #7	$20.45	3.331%	$21.1312	$21.13	$21.15	$21.10
7 purchase totals =	$804.88		$862.8797	$862.88	$862.85	$862.90