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	$125.70	12.725%	$141.6953	$141.70	$141.70	$141.70
Purchase #2	$39.51	7.306%	$42.3966	$42.40	$42.40	$42.40
Purchase #3	$239.59	7.163%	$256.7518	$256.75	$256.75	$256.80
Purchase #4	$137.40	9.544%	$150.5135	$150.51	$150.50	$150.50
Purchase #5	$102.49	10.639%	$113.3939	$113.39	$113.40	$113.40
Purchase #6	$94.86	5.230%	$99.8212	$99.82	$99.80	$99.80
Purchase #7	$115.48	4.363%	$120.5184	$120.52	$120.50	$120.50
7 purchase totals =	$855.03		$925.0907	$925.09	$925.05	$925.10