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	$117.82	4.255%	$122.8332	$122.83	$122.85	$122.80
Purchase #2	$40.58	6.718%	$43.3062	$43.31	$43.30	$43.30
Purchase #3	$94.47	3.207%	$97.4997	$97.50	$97.50	$97.50
Purchase #4	$5.85	10.684%	$6.475	$6.48	$6.50	$6.50
Purchase #5	$103.68	7.705%	$111.6685	$111.67	$111.65	$111.70
Purchase #6	$185.69	5.676%	$196.2298	$196.23	$196.25	$196.20
Purchase #7	$73.61	8.523%	$79.8838	$79.88	$79.90	$79.90
7 purchase totals =	$621.70		$657.8962	$657.90	$657.95	$657.90