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	$66.85	8.828%	$72.7515	$72.75	$72.75	$72.80
Purchase #2	$239.29	10.283%	$263.8962	$263.90	$263.90	$263.90
Purchase #3	$57.47	6.552%	$61.2354	$61.24	$61.25	$61.20
Purchase #4	$40.95	13.375%	$46.4271	$46.43	$46.45	$46.40
Purchase #5	$165.53	4.629%	$173.1924	$173.19	$173.20	$173.20
Purchase #6	$147.64	11.440%	$164.53	$164.53	$164.55	$164.50
Purchase #7	$147.29	8.267%	$159.4665	$159.47	$159.45	$159.50
7 purchase totals =	$865.02		$941.4991	$941.51	$941.55	$941.50