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	$118.88	13.461%	$134.8824	$134.88	$134.90	$134.90
Purchase #2	$235.88	3.117%	$243.2324	$243.23	$243.25	$243.20
Purchase #3	$246.57	11.333%	$274.5138	$274.51	$274.50	$274.50
Purchase #4	$161.90	4.681%	$169.4785	$169.48	$169.50	$169.50
Purchase #5	$56.90	8.235%	$61.5857	$61.59	$61.60	$61.60
Purchase #6	$112.92	10.349%	$124.6061	$124.61	$124.60	$124.60
Purchase #7	$115.92	7.162%	$124.2222	$124.22	$124.20	$124.20
7 purchase totals =	$1,048.97		$1,132.5211	$1,132.52	$1,132.55	$1,132.50