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	$112.31	5.244%	$118.1995	$118.20	$118.20	$118.20
Purchase #2	$50.42	11.698%	$56.3181	$56.32	$56.30	$56.30
Purchase #3	$80.25	5.685%	$84.8122	$84.81	$84.80	$84.80
Purchase #4	$12.72	9.588%	$13.9396	$13.94	$13.95	$13.90
Purchase #5	$42.59	5.862%	$45.0866	$45.09	$45.10	$45.10
Purchase #6	$123.94	10.764%	$137.2809	$137.28	$137.30	$137.30
Purchase #7	$154.41	11.693%	$172.4652	$172.47	$172.45	$172.50
7 purchase totals =	$576.64		$628.1021	$628.11	$628.10	$628.10