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	$76.47	12.553%	$86.0693	$86.07	$86.05	$86.10
Purchase #2	$37.34	13.302%	$42.307	$42.31	$42.30	$42.30
Purchase #3	$63.28	4.401%	$66.065	$66.07	$66.05	$66.10
Purchase #4	$198.70	9.403%	$217.3838	$217.38	$217.40	$217.40
Purchase #5	$208.31	8.338%	$225.6789	$225.68	$225.70	$225.70
Purchase #6	$217.80	7.622%	$234.4007	$234.40	$234.40	$234.40
Purchase #7	$53.32	11.452%	$59.4262	$59.43	$59.45	$59.40
7 purchase totals =	$855.22		$931.3309	$931.34	$931.35	$931.40