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	$121.67	7.480%	$130.7709	$130.77	$130.75	$130.80
Purchase #2	$176.61	11.257%	$196.491	$196.49	$196.50	$196.50
Purchase #3	$124.32	6.734%	$132.6917	$132.69	$132.70	$132.70
Purchase #4	$111.86	6.213%	$118.8099	$118.81	$118.80	$118.80
Purchase #5	$193.37	6.186%	$205.3319	$205.33	$205.35	$205.30
Purchase #6	$90.90	5.590%	$95.9813	$95.98	$96.00	$96.00
Purchase #7	$106.82	9.262%	$116.7137	$116.71	$116.70	$116.70
7 purchase totals =	$925.55		$996.7904	$996.78	$996.80	$996.80