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	$185.41	7.748%	$199.7756	$199.78	$199.80	$199.80
Purchase #2	$188.69	4.352%	$196.9018	$196.90	$196.90	$196.90
Purchase #3	$189.73	7.321%	$203.6201	$203.62	$203.60	$203.60
Purchase #4	$91.59	11.602%	$102.2163	$102.22	$102.20	$102.20
Purchase #5	$143.32	10.619%	$158.5392	$158.54	$158.55	$158.50
Purchase #6	$63.37	10.797%	$70.2121	$70.21	$70.20	$70.20
Purchase #7	$184.54	13.569%	$209.5802	$209.58	$209.60	$209.60
7 purchase totals =	$1,046.65		$1,140.8453	$1,140.85	$1,140.85	$1,140.80