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	$235.28	5.592%	$248.4369	$248.44	$248.45	$248.40
Purchase #2	$138.42	7.362%	$148.6105	$148.61	$148.60	$148.60
Purchase #3	$200.54	11.128%	$222.8561	$222.86	$222.85	$222.90
Purchase #4	$52.40	8.119%	$56.6544	$56.65	$56.65	$56.70
Purchase #5	$30.66	6.231%	$32.5704	$32.57	$32.55	$32.60
Purchase #6	$193.30	12.383%	$217.2363	$217.24	$217.25	$217.20
Purchase #7	$68.80	3.333%	$71.0931	$71.09	$71.10	$71.10
7 purchase totals =	$919.40		$997.4577	$997.46	$997.45	$997.50