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	$250.89	6.576%	$267.3885	$267.39	$267.40	$267.40
Purchase #2	$67.99	6.801%	$72.614	$72.61	$72.60	$72.60
Purchase #3	$6.48	13.680%	$7.3665	$7.37	$7.35	$7.40
Purchase #4	$132.53	13.664%	$150.6389	$150.64	$150.65	$150.60
Purchase #5	$146.71	8.673%	$159.4342	$159.43	$159.45	$159.40
Purchase #6	$148.54	4.612%	$155.3907	$155.39	$155.40	$155.40
Purchase #7	$199.64	6.716%	$213.0478	$213.05	$213.05	$213.00
7 purchase totals =	$952.78		$1,025.8806	$1,025.88	$1,025.90	$1,025.80