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	$43.94	4.748%	$46.0263	$46.03	$46.05	$46.00
Purchase #2	$138.96	5.682%	$146.8557	$146.86	$146.85	$146.90
Purchase #3	$76.96	4.254%	$80.2339	$80.23	$80.25	$80.20
Purchase #4	$29.40	10.485%	$32.4826	$32.48	$32.50	$32.50
Purchase #5	$74.70	11.640%	$83.3951	$83.40	$83.40	$83.40
Purchase #6	$27.85	11.422%	$31.031	$31.03	$31.05	$31.00
Purchase #7	$231.34	9.564%	$253.4654	$253.47	$253.45	$253.50
7 purchase totals =	$623.15		$673.4900	$673.50	$673.55	$673.50