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	$153.65	7.783%	$165.6086	$165.61	$165.60	$165.60
Purchase #2	$102.50	8.358%	$111.067	$111.07	$111.05	$111.10
Purchase #3	$142.52	10.284%	$157.1768	$157.18	$157.20	$157.20
Purchase #4	$203.88	13.524%	$231.4527	$231.45	$231.45	$231.50
Purchase #5	$167.57	9.287%	$183.1322	$183.13	$183.15	$183.10
Purchase #6	$70.78	7.690%	$76.223	$76.22	$76.20	$76.20
Purchase #7	$18.49	13.294%	$20.9481	$20.95	$20.95	$20.90
7 purchase totals =	$859.39		$945.6084	$945.61	$945.60	$945.60