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	$207.67	4.419%	$216.8469	$216.85	$216.85	$216.80
Purchase #2	$195.84	13.789%	$222.8444	$222.84	$222.85	$222.80
Purchase #3	$84.88	12.594%	$95.5698	$95.57	$95.55	$95.60
Purchase #4	$117.86	4.850%	$123.5762	$123.58	$123.60	$123.60
Purchase #5	$124.57	13.192%	$141.0033	$141.00	$141.00	$141.00
Purchase #6	$60.87	11.464%	$67.8481	$67.85	$67.85	$67.80
Purchase #7	$229.63	11.571%	$256.2005	$256.20	$256.20	$256.20
7 purchase totals =	$1,021.32		$1,123.8892	$1,123.89	$1,123.90	$1,123.80