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	$34.66	6.341%	$36.8578	$36.86	$36.85	$36.90
Purchase #2	$58.67	4.850%	$61.5155	$61.52	$61.50	$61.50
Purchase #3	$28.90	10.862%	$32.0391	$32.04	$32.05	$32.00
Purchase #4	$83.60	9.175%	$91.2703	$91.27	$91.25	$91.30
Purchase #5	$86.37	7.198%	$92.5869	$92.59	$92.60	$92.60
Purchase #6	$13.76	9.204%	$15.0265	$15.03	$15.05	$15.00
Purchase #7	$138.38	12.533%	$155.7232	$155.72	$155.70	$155.70
7 purchase totals =	$444.34		$485.0193	$485.03	$485.00	$485.00