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	$208.85	8.299%	$226.1825	$226.18	$226.20	$226.20
Purchase #2	$142.72	11.854%	$159.638	$159.64	$159.65	$159.60
Purchase #3	$47.31	7.372%	$50.7977	$50.80	$50.80	$50.80
Purchase #4	$103.57	7.684%	$111.5283	$111.53	$111.55	$111.50
Purchase #5	$218.50	12.601%	$246.0332	$246.03	$246.05	$246.00
Purchase #6	$100.81	10.586%	$111.4817	$111.48	$111.50	$111.50
Purchase #7	$130.71	5.563%	$137.9814	$137.98	$138.00	$138.00
7 purchase totals =	$952.47		$1,043.6428	$1,043.64	$1,043.75	$1,043.60