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	$18.81	9.507%	$20.5983	$20.60	$20.60	$20.60
Purchase #2	$10.78	4.693%	$11.2859	$11.29	$11.30	$11.30
Purchase #3	$174.63	5.280%	$183.8505	$183.85	$183.85	$183.90
Purchase #4	$169.43	12.548%	$190.6901	$190.69	$190.70	$190.70
Purchase #5	$230.99	5.848%	$244.4983	$244.50	$244.50	$244.50
Purchase #6	$240.25	13.683%	$273.1234	$273.12	$273.10	$273.10
Purchase #7	$130.43	7.215%	$139.8405	$139.84	$139.85	$139.80
7 purchase totals =	$975.32		$1,063.8870	$1,063.89	$1,063.90	$1,063.90