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	$158.67	8.650%	$172.395	$172.40	$172.40	$172.40
Purchase #2	$119.66	5.190%	$125.8704	$125.87	$125.85	$125.90
Purchase #3	$243.85	13.607%	$277.0307	$277.03	$277.05	$277.00
Purchase #4	$187.55	6.144%	$199.0731	$199.07	$199.05	$199.10
Purchase #5	$77.45	8.312%	$83.8876	$83.89	$83.90	$83.90
Purchase #6	$169.72	12.175%	$190.3834	$190.38	$190.40	$190.40
Purchase #7	$47.47	11.702%	$53.0249	$53.02	$53.00	$53.00
7 purchase totals =	$1,004.37		$1,101.6651	$1,101.66	$1,101.65	$1,101.70