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	$152.56	9.624%	$167.2424	$167.24	$167.25	$167.20
Purchase #2	$72.72	10.707%	$80.5061	$80.51	$80.50	$80.50
Purchase #3	$186.32	10.811%	$206.4631	$206.46	$206.45	$206.50
Purchase #4	$31.59	9.587%	$34.6185	$34.62	$34.60	$34.60
Purchase #5	$184.44	8.621%	$200.3406	$200.34	$200.35	$200.30
Purchase #6	$77.52	10.681%	$85.7999	$85.80	$85.80	$85.80
Purchase #7	$241.89	12.167%	$271.3208	$271.32	$271.30	$271.30
7 purchase totals =	$947.04		$1,046.2914	$1,046.29	$1,046.25	$1,046.20