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	$208.45	12.559%	$234.6292	$234.63	$234.65	$234.60
Purchase #2	$132.48	6.853%	$141.5589	$141.56	$141.55	$141.60
Purchase #3	$153.86	8.140%	$166.3842	$166.38	$166.40	$166.40
Purchase #4	$124.81	4.345%	$130.233	$130.23	$130.25	$130.20
Purchase #5	$68.67	11.256%	$76.3995	$76.40	$76.40	$76.40
Purchase #6	$246.33	3.547%	$255.0673	$255.07	$255.05	$255.10
Purchase #7	$14.80	3.363%	$15.2977	$15.30	$15.30	$15.30
7 purchase totals =	$949.40		$1,019.5698	$1,019.57	$1,019.60	$1,019.60