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	$169.50	10.434%	$187.1856	$187.19	$187.20	$187.20
Purchase #2	$248.50	10.670%	$275.015	$275.02	$275.00	$275.00
Purchase #3	$143.82	5.162%	$151.244	$151.24	$151.25	$151.20
Purchase #4	$124.76	4.863%	$130.8271	$130.83	$130.85	$130.80
Purchase #5	$13.28	8.591%	$14.4209	$14.42	$14.40	$14.40
Purchase #6	$102.32	5.811%	$108.2658	$108.27	$108.25	$108.30
Purchase #7	$236.72	3.813%	$245.7461	$245.75	$245.75	$245.70
7 purchase totals =	$1,038.90		$1,112.7045	$1,112.72	$1,112.70	$1,112.60