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	$64.53	4.156%	$67.2119	$67.21	$67.20	$67.20
Purchase #2	$95.42	9.549%	$104.5317	$104.53	$104.55	$104.50
Purchase #3	$231.62	9.691%	$254.0663	$254.07	$254.05	$254.10
Purchase #4	$148.35	12.863%	$167.4323	$167.43	$167.45	$167.40
Purchase #5	$205.44	5.428%	$216.5913	$216.59	$216.60	$216.60
Purchase #6	$83.79	6.731%	$89.4299	$89.43	$89.45	$89.40
Purchase #7	$117.39	7.214%	$125.8585	$125.86	$125.85	$125.90
7 purchase totals =	$946.54		$1,025.1219	$1,025.12	$1,025.15	$1,025.10