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	$41.95	9.127%	$45.7788	$45.78	$45.80	$45.80
Purchase #2	$165.99	13.224%	$187.9405	$187.94	$187.95	$187.90
Purchase #3	$183.77	7.149%	$196.9077	$196.91	$196.90	$196.90
Purchase #4	$63.79	11.333%	$71.0193	$71.02	$71.00	$71.00
Purchase #5	$114.95	4.811%	$120.4802	$120.48	$120.50	$120.50
Purchase #6	$164.26	7.233%	$176.1409	$176.14	$176.15	$176.10
Purchase #7	$160.42	7.707%	$172.7836	$172.78	$172.80	$172.80
7 purchase totals =	$895.13		$971.0510	$971.05	$971.10	$971.00