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	$50.61	13.350%	$57.3664	$57.37	$57.35	$57.40
Purchase #2	$89.93	9.231%	$98.2314	$98.23	$98.25	$98.20
Purchase #3	$134.60	6.430%	$143.2548	$143.25	$143.25	$143.30
Purchase #4	$161.51	4.274%	$168.4129	$168.41	$168.40	$168.40
Purchase #5	$206.65	3.228%	$213.3207	$213.32	$213.30	$213.30
Purchase #6	$208.59	11.358%	$232.2817	$232.28	$232.30	$232.30
Purchase #7	$48.34	13.484%	$54.8582	$54.86	$54.85	$54.90
7 purchase totals =	$900.23		$967.7261	$967.72	$967.70	$967.80