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	$172.95	10.812%	$191.6494	$191.65	$191.65	$191.60
Purchase #2	$216.91	11.813%	$242.5336	$242.53	$242.55	$242.50
Purchase #3	$83.67	8.181%	$90.515	$90.52	$90.50	$90.50
Purchase #4	$187.84	11.562%	$209.5581	$209.56	$209.55	$209.60
Purchase #5	$105.42	13.121%	$119.2522	$119.25	$119.25	$119.30
Purchase #6	$39.60	11.228%	$44.0463	$44.05	$44.05	$44.00
Purchase #7	$239.50	9.461%	$262.1591	$262.16	$262.15	$262.20
7 purchase totals =	$1,045.89		$1,159.7137	$1,159.72	$1,159.70	$1,159.70