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	$239.48	6.552%	$255.1707	$255.17	$255.15	$255.20
Purchase #2	$155.95	11.640%	$174.1026	$174.10	$174.10	$174.10
Purchase #3	$95.71	10.579%	$105.8352	$105.84	$105.85	$105.80
Purchase #4	$248.89	13.444%	$282.3508	$282.35	$282.35	$282.40
Purchase #5	$181.81	9.561%	$199.1929	$199.19	$199.20	$199.20
Purchase #6	$154.61	13.448%	$175.402	$175.40	$175.40	$175.40
Purchase #7	$168.42	10.162%	$185.5348	$185.53	$185.55	$185.50
7 purchase totals =	$1,244.87		$1,377.5890	$1,377.58	$1,377.60	$1,377.60