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	$141.42	6.564%	$150.7028	$150.70	$150.70	$150.70
Purchase #2	$58.89	13.518%	$66.8508	$66.85	$66.85	$66.90
Purchase #3	$84.88	10.395%	$93.7033	$93.70	$93.70	$93.70
Purchase #4	$215.52	10.749%	$238.6862	$238.69	$238.70	$238.70
Purchase #5	$144.88	13.822%	$164.9053	$164.91	$164.90	$164.90
Purchase #6	$134.89	5.525%	$142.3427	$142.34	$142.35	$142.30
Purchase #7	$106.48	10.142%	$117.2792	$117.28	$117.30	$117.30
7 purchase totals =	$886.96		$974.4703	$974.47	$974.50	$974.50