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	$172.86	13.553%	$196.2877	$196.29	$196.30	$196.30
Purchase #2	$55.93	3.203%	$57.7214	$57.72	$57.70	$57.70
Purchase #3	$151.61	5.406%	$159.806	$159.81	$159.80	$159.80
Purchase #4	$19.37	10.500%	$21.4039	$21.40	$21.40	$21.40
Purchase #5	$83.70	4.496%	$87.4632	$87.46	$87.45	$87.50
Purchase #6	$243.87	11.379%	$271.62	$271.62	$271.60	$271.60
Purchase #7	$138.40	12.663%	$155.9256	$155.93	$155.95	$155.90
7 purchase totals =	$865.74		$950.2278	$950.23	$950.20	$950.20