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	$130.81	10.867%	$145.0251	$145.03	$145.05	$145.00
Purchase #2	$137.36	11.110%	$152.6207	$152.62	$152.60	$152.60
Purchase #3	$246.61	3.799%	$255.9787	$255.98	$256.00	$256.00
Purchase #4	$11.67	10.300%	$12.872	$12.87	$12.85	$12.90
Purchase #5	$77.85	6.852%	$83.1843	$83.18	$83.20	$83.20
Purchase #6	$193.67	3.204%	$199.8752	$199.88	$199.90	$199.90
Purchase #7	$94.55	11.767%	$105.6757	$105.68	$105.70	$105.70
7 purchase totals =	$892.52		$955.2317	$955.24	$955.30	$955.30