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	$78.78	5.113%	$82.808	$82.81	$82.80	$82.80
Purchase #2	$182.56	9.212%	$199.3774	$199.38	$199.40	$199.40
Purchase #3	$122.58	6.133%	$130.0978	$130.10	$130.10	$130.10
Purchase #4	$12.25	9.155%	$13.3715	$13.37	$13.35	$13.40
Purchase #5	$229.45	9.587%	$251.4474	$251.45	$251.45	$251.40
Purchase #6	$84.70	12.211%	$95.0427	$95.04	$95.05	$95.00
Purchase #7	$231.37	10.796%	$256.3487	$256.35	$256.35	$256.30
7 purchase totals =	$941.69		$1,028.4935	$1,028.50	$1,028.50	$1,028.40