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	$40.34	6.610%	$43.0065	$43.01	$43.00	$43.00
Purchase #2	$117.95	11.637%	$131.6758	$131.68	$131.70	$131.70
Purchase #3	$68.81	4.110%	$71.6381	$71.64	$71.65	$71.60
Purchase #4	$143.57	7.846%	$154.8345	$154.83	$154.85	$154.80
Purchase #5	$5.59	10.403%	$6.1715	$6.17	$6.15	$6.20
Purchase #6	$180.30	11.146%	$200.3962	$200.40	$200.40	$200.40
Purchase #7	$134.96	8.270%	$146.1212	$146.12	$146.10	$146.10
7 purchase totals =	$691.52		$753.8438	$753.85	$753.85	$753.80