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	$214.45	3.443%	$221.8335	$221.83	$221.85	$221.80
Purchase #2	$80.57	12.846%	$90.92	$90.92	$90.90	$90.90
Purchase #3	$72.89	3.861%	$75.7043	$75.70	$75.70	$75.70
Purchase #4	$230.99	8.377%	$250.34	$250.34	$250.35	$250.30
Purchase #5	$223.48	9.493%	$244.695	$244.70	$244.70	$244.70
Purchase #6	$66.79	8.580%	$72.5206	$72.52	$72.50	$72.50
Purchase #7	$232.38	10.428%	$256.6126	$256.61	$256.60	$256.60
7 purchase totals =	$1,121.55		$1,212.6260	$1,212.62	$1,212.60	$1,212.50