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	$247.58	9.598%	$271.3427	$271.34	$271.35	$271.30
Purchase #2	$208.95	11.322%	$232.6073	$232.61	$232.60	$232.60
Purchase #3	$222.84	9.320%	$243.6087	$243.61	$243.60	$243.60
Purchase #4	$109.49	6.754%	$116.885	$116.89	$116.90	$116.90
Purchase #5	$36.49	7.228%	$39.1275	$39.13	$39.15	$39.10
Purchase #6	$128.44	13.306%	$145.5302	$145.53	$145.55	$145.50
Purchase #7	$43.60	3.466%	$45.1112	$45.11	$45.10	$45.10
7 purchase totals =	$997.39		$1,094.2126	$1,094.22	$1,094.25	$1,094.10