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	$208.54	8.173%	$225.584	$225.58	$225.60	$225.60
Purchase #2	$246.30	13.311%	$279.085	$279.09	$279.10	$279.10
Purchase #3	$79.55	13.162%	$90.0204	$90.02	$90.00	$90.00
Purchase #4	$164.48	12.549%	$185.1206	$185.12	$185.10	$185.10
Purchase #5	$38.81	8.402%	$42.0708	$42.07	$42.05	$42.10
Purchase #6	$141.38	12.506%	$159.061	$159.06	$159.05	$159.10
Purchase #7	$244.69	10.116%	$269.4428	$269.44	$269.45	$269.40
7 purchase totals =	$1,123.75		$1,250.3846	$1,250.38	$1,250.35	$1,250.40