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	$222.93	11.446%	$248.4466	$248.45	$248.45	$248.40
Purchase #2	$148.48	7.390%	$159.4527	$159.45	$159.45	$159.50
Purchase #3	$37.89	5.759%	$40.0721	$40.07	$40.05	$40.10
Purchase #4	$217.81	10.193%	$240.0114	$240.01	$240.00	$240.00
Purchase #5	$28.68	8.211%	$31.0349	$31.03	$31.05	$31.00
Purchase #6	$38.95	3.864%	$40.455	$40.46	$40.45	$40.50
Purchase #7	$217.55	9.131%	$237.4145	$237.41	$237.40	$237.40
7 purchase totals =	$912.29		$996.8872	$996.88	$996.85	$996.90