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	$66.32	3.591%	$68.7016	$68.70	$68.70	$68.70
Purchase #2	$194.57	5.740%	$205.7383	$205.74	$205.75	$205.70
Purchase #3	$92.83	11.266%	$103.2882	$103.29	$103.30	$103.30
Purchase #4	$90.96	10.273%	$100.3043	$100.30	$100.30	$100.30
Purchase #5	$220.35	6.364%	$234.3731	$234.37	$234.35	$234.40
Purchase #6	$105.76	5.117%	$111.1717	$111.17	$111.15	$111.20
Purchase #7	$136.93	11.511%	$152.692	$152.69	$152.70	$152.70
7 purchase totals =	$907.72		$976.2692	$976.26	$976.25	$976.30