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	$241.46	7.746%	$260.1635	$260.16	$260.15	$260.20
Purchase #2	$224.51	3.519%	$232.4105	$232.41	$232.40	$232.40
Purchase #3	$92.97	8.400%	$100.7795	$100.78	$100.80	$100.80
Purchase #4	$71.83	6.496%	$76.4961	$76.50	$76.50	$76.50
Purchase #5	$119.43	9.230%	$130.4534	$130.45	$130.45	$130.50
Purchase #6	$67.78	8.342%	$73.4342	$73.43	$73.45	$73.40
Purchase #7	$156.63	5.657%	$165.4906	$165.49	$165.50	$165.50
7 purchase totals =	$974.61		$1,039.2278	$1,039.22	$1,039.25	$1,039.30