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	$127.46	5.743%	$134.78	$134.78	$134.80	$134.80
Purchase #2	$19.34	3.790%	$20.073	$20.07	$20.05	$20.10
Purchase #3	$66.28	7.165%	$71.029	$71.03	$71.05	$71.00
Purchase #4	$18.90	12.138%	$21.1941	$21.19	$21.20	$21.20
Purchase #5	$131.35	13.726%	$149.3791	$149.38	$149.40	$149.40
Purchase #6	$100.70	4.750%	$105.4833	$105.48	$105.50	$105.50
Purchase #7	$75.34	4.195%	$78.5005	$78.50	$78.50	$78.50
7 purchase totals =	$539.37		$580.4390	$580.43	$580.50	$580.50