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	$142.71	6.679%	$152.2416	$152.24	$152.25	$152.20
Purchase #2	$53.95	13.783%	$61.3859	$61.39	$61.40	$61.40
Purchase #3	$39.48	3.649%	$40.9206	$40.92	$40.90	$40.90
Purchase #4	$90.58	3.141%	$93.4251	$93.43	$93.45	$93.40
Purchase #5	$131.70	4.515%	$137.6463	$137.65	$137.65	$137.60
Purchase #6	$59.95	10.274%	$66.1093	$66.11	$66.10	$66.10
Purchase #7	$205.51	12.429%	$231.0528	$231.05	$231.05	$231.10
7 purchase totals =	$723.88		$782.7816	$782.79	$782.80	$782.70