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	$131.35	11.317%	$146.2149	$146.21	$146.20	$146.20
Purchase #2	$151.43	8.428%	$164.1925	$164.19	$164.20	$164.20
Purchase #3	$154.42	4.221%	$160.9381	$160.94	$160.95	$160.90
Purchase #4	$43.63	4.310%	$45.5105	$45.51	$45.50	$45.50
Purchase #5	$230.31	3.387%	$238.1106	$238.11	$238.10	$238.10
Purchase #6	$201.43	3.208%	$207.8919	$207.89	$207.90	$207.90
Purchase #7	$55.87	9.201%	$61.0106	$61.01	$61.00	$61.00
7 purchase totals =	$968.44		$1,023.8691	$1,023.86	$1,023.85	$1,023.80