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	$204.96	5.206%	$215.6302	$215.63	$215.65	$215.60
Purchase #2	$213.39	13.438%	$242.0653	$242.07	$242.05	$242.10
Purchase #3	$137.86	6.561%	$146.905	$146.91	$146.90	$146.90
Purchase #4	$37.32	8.129%	$40.3537	$40.35	$40.35	$40.40
Purchase #5	$193.47	7.669%	$208.3072	$208.31	$208.30	$208.30
Purchase #6	$175.95	6.779%	$187.8777	$187.88	$187.90	$187.90
Purchase #7	$73.51	11.576%	$82.0195	$82.02	$82.00	$82.00
7 purchase totals =	$1,036.46		$1,123.1586	$1,123.17	$1,123.15	$1,123.20