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	$84.59	12.703%	$95.3355	$95.34	$95.35	$95.30
Purchase #2	$178.51	10.297%	$196.8912	$196.89	$196.90	$196.90
Purchase #3	$54.38	9.797%	$59.7076	$59.71	$59.70	$59.70
Purchase #4	$11.80	7.602%	$12.697	$12.70	$12.70	$12.70
Purchase #5	$155.75	8.750%	$169.3781	$169.38	$169.40	$169.40
Purchase #6	$49.90	7.187%	$53.4863	$53.49	$53.50	$53.50
Purchase #7	$218.49	3.467%	$226.065	$226.07	$226.05	$226.10
7 purchase totals =	$753.42		$813.5607	$813.58	$813.60	$813.60