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	$246.36	7.482%	$264.7927	$264.79	$264.80	$264.80
Purchase #2	$159.38	13.503%	$180.9011	$180.90	$180.90	$180.90
Purchase #3	$100.67	10.793%	$111.5353	$111.54	$111.55	$111.50
Purchase #4	$57.89	5.406%	$61.0195	$61.02	$61.00	$61.00
Purchase #5	$93.69	13.686%	$106.5124	$106.51	$106.50	$106.50
Purchase #6	$34.42	5.769%	$36.4057	$36.41	$36.40	$36.40
Purchase #7	$180.54	5.445%	$190.3704	$190.37	$190.35	$190.40
7 purchase totals =	$872.95		$951.5371	$951.54	$951.50	$951.50