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	$130.31	10.527%	$144.0277	$144.03	$144.05	$144.00
Purchase #2	$40.89	13.304%	$46.33	$46.33	$46.35	$46.30
Purchase #3	$249.50	10.374%	$275.3831	$275.38	$275.40	$275.40
Purchase #4	$78.60	8.186%	$85.0342	$85.03	$85.05	$85.00
Purchase #5	$198.94	6.768%	$212.4043	$212.40	$212.40	$212.40
Purchase #6	$221.38	9.595%	$242.6214	$242.62	$242.60	$242.60
Purchase #7	$213.76	5.593%	$225.7156	$225.72	$225.70	$225.70
7 purchase totals =	$1,133.38		$1,231.5163	$1,231.51	$1,231.55	$1,231.40