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	$197.42	5.833%	$208.9355	$208.94	$208.95	$208.90
Purchase #2	$62.95	6.617%	$67.1154	$67.12	$67.10	$67.10
Purchase #3	$199.71	11.460%	$222.5968	$222.60	$222.60	$222.60
Purchase #4	$41.73	12.804%	$47.0731	$47.07	$47.05	$47.10
Purchase #5	$182.57	4.184%	$190.2087	$190.21	$190.20	$190.20
Purchase #6	$7.29	4.476%	$7.6163	$7.62	$7.60	$7.60
Purchase #7	$104.37	8.265%	$112.9962	$113.00	$113.00	$113.00
7 purchase totals =	$796.04		$856.5420	$856.56	$856.50	$856.50