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	$200.95	12.255%	$225.5764	$225.58	$225.60	$225.60
Purchase #2	$122.52	3.738%	$127.0998	$127.10	$127.10	$127.10
Purchase #3	$222.66	11.440%	$248.1323	$248.13	$248.15	$248.10
Purchase #4	$236.88	12.571%	$266.6582	$266.66	$266.65	$266.70
Purchase #5	$63.45	12.362%	$71.2937	$71.29	$71.30	$71.30
Purchase #6	$193.76	7.582%	$208.4509	$208.45	$208.45	$208.50
Purchase #7	$41.35	13.330%	$46.862	$46.86	$46.85	$46.90
7 purchase totals =	$1,081.57		$1,194.0733	$1,194.07	$1,194.10	$1,194.20