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	$116.45	13.388%	$132.0403	$132.04	$132.05	$132.00
Purchase #2	$36.88	9.597%	$40.4194	$40.42	$40.40	$40.40
Purchase #3	$244.25	3.591%	$253.021	$253.02	$253.00	$253.00
Purchase #4	$98.68	6.261%	$104.8584	$104.86	$104.85	$104.90
Purchase #5	$82.67	9.163%	$90.2451	$90.25	$90.25	$90.20
Purchase #6	$221.41	10.544%	$244.7555	$244.76	$244.75	$244.80
Purchase #7	$73.67	13.404%	$83.5447	$83.54	$83.55	$83.50
7 purchase totals =	$874.01		$948.8844	$948.89	$948.85	$948.80