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	$148.72	13.684%	$169.0708	$169.07	$169.05	$169.10
Purchase #2	$95.72	3.854%	$99.409	$99.41	$99.40	$99.40
Purchase #3	$37.39	13.510%	$42.4414	$42.44	$42.45	$42.40
Purchase #4	$38.70	3.760%	$40.1551	$40.16	$40.15	$40.20
Purchase #5	$246.39	6.277%	$261.8559	$261.86	$261.85	$261.90
Purchase #6	$208.90	10.613%	$231.0706	$231.07	$231.05	$231.10
Purchase #7	$249.69	11.845%	$279.2658	$279.27	$279.25	$279.30
7 purchase totals =	$1,025.51		$1,123.2686	$1,123.28	$1,123.20	$1,123.40