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	$55.34	11.230%	$61.5547	$61.55	$61.55	$61.60
Purchase #2	$113.68	10.497%	$125.613	$125.61	$125.60	$125.60
Purchase #3	$205.29	3.836%	$213.1649	$213.16	$213.15	$213.20
Purchase #4	$39.64	7.196%	$42.4925	$42.49	$42.50	$42.50
Purchase #5	$70.31	13.434%	$79.7554	$79.76	$79.75	$79.80
Purchase #6	$78.47	5.818%	$83.0354	$83.04	$83.05	$83.00
Purchase #7	$111.69	11.674%	$124.7287	$124.73	$124.75	$124.70
7 purchase totals =	$674.42		$730.3446	$730.34	$730.35	$730.40