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	$213.44	6.536%	$227.3904	$227.39	$227.40	$227.40
Purchase #2	$21.66	3.369%	$22.3897	$22.39	$22.40	$22.40
Purchase #3	$72.85	7.356%	$78.2088	$78.21	$78.20	$78.20
Purchase #4	$204.77	9.158%	$223.5228	$223.52	$223.50	$223.50
Purchase #5	$48.86	13.391%	$55.4028	$55.40	$55.40	$55.40
Purchase #6	$20.85	12.279%	$23.4102	$23.41	$23.40	$23.40
Purchase #7	$42.85	12.217%	$48.085	$48.09	$48.10	$48.10
7 purchase totals =	$625.28		$678.4097	$678.41	$678.40	$678.40