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	$210.56	4.174%	$219.3488	$219.35	$219.35	$219.30
Purchase #2	$110.89	12.105%	$124.3132	$124.31	$124.30	$124.30
Purchase #3	$196.94	13.471%	$223.4698	$223.47	$223.45	$223.50
Purchase #4	$9.49	12.391%	$10.6659	$10.67	$10.65	$10.70
Purchase #5	$123.79	10.551%	$136.8511	$136.85	$136.85	$136.90
Purchase #6	$105.37	4.672%	$110.2929	$110.29	$110.30	$110.30
Purchase #7	$205.51	5.443%	$216.6959	$216.70	$216.70	$216.70
7 purchase totals =	$962.55		$1,041.6376	$1,041.64	$1,041.60	$1,041.70