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	$21.74	4.246%	$22.6631	$22.66	$22.65	$22.70
Purchase #2	$213.77	11.178%	$237.6652	$237.67	$237.65	$237.70
Purchase #3	$91.92	10.231%	$101.3243	$101.32	$101.30	$101.30
Purchase #4	$85.84	11.496%	$95.7082	$95.71	$95.70	$95.70
Purchase #5	$53.40	11.331%	$59.4508	$59.45	$59.45	$59.50
Purchase #6	$32.89	10.763%	$36.43	$36.43	$36.45	$36.40
Purchase #7	$41.71	4.350%	$43.5244	$43.52	$43.50	$43.50
7 purchase totals =	$541.27		$596.7660	$596.76	$596.70	$596.80