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	$220.50	6.341%	$234.4819	$234.48	$234.50	$234.50
Purchase #2	$148.43	11.503%	$165.5039	$165.50	$165.50	$165.50
Purchase #3	$241.32	13.441%	$273.7558	$273.76	$273.75	$273.80
Purchase #4	$95.48	5.660%	$100.8842	$100.88	$100.90	$100.90
Purchase #5	$11.50	9.721%	$12.6179	$12.62	$12.60	$12.60
Purchase #6	$153.65	7.502%	$165.1768	$165.18	$165.20	$165.20
Purchase #7	$232.95	6.554%	$248.2175	$248.22	$248.20	$248.20
7 purchase totals =	$1,103.83		$1,200.6380	$1,200.64	$1,200.65	$1,200.70