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	$240.45	10.810%	$266.4426	$266.44	$266.45	$266.40
Purchase #2	$199.59	3.118%	$205.8132	$205.81	$205.80	$205.80
Purchase #3	$83.80	5.344%	$88.2783	$88.28	$88.30	$88.30
Purchase #4	$250.80	10.350%	$276.7578	$276.76	$276.75	$276.80
Purchase #5	$40.43	12.195%	$45.3604	$45.36	$45.35	$45.40
Purchase #6	$188.33	4.134%	$196.1156	$196.12	$196.10	$196.10
Purchase #7	$120.79	13.680%	$137.3141	$137.31	$137.30	$137.30
7 purchase totals =	$1,124.19		$1,216.0820	$1,216.08	$1,216.05	$1,216.10