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	$100.53	11.840%	$112.4328	$112.43	$112.45	$112.40
Purchase #2	$53.69	8.142%	$58.0614	$58.06	$58.05	$58.10
Purchase #3	$11.32	7.445%	$12.1628	$12.16	$12.15	$12.20
Purchase #4	$41.97	7.571%	$45.1475	$45.15	$45.15	$45.10
Purchase #5	$28.32	13.142%	$32.0418	$32.04	$32.05	$32.00
Purchase #6	$234.72	11.825%	$262.4756	$262.48	$262.50	$262.50
Purchase #7	$142.30	10.649%	$157.4535	$157.45	$157.45	$157.50
7 purchase totals =	$612.85		$679.7754	$679.77	$679.80	$679.80