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	$9.41	10.400%	$10.3886	$10.39	$10.40	$10.40
Purchase #2	$56.71	10.603%	$62.723	$62.72	$62.70	$62.70
Purchase #3	$76.53	9.615%	$83.8884	$83.89	$83.90	$83.90
Purchase #4	$30.85	9.513%	$33.7848	$33.78	$33.80	$33.80
Purchase #5	$217.54	4.680%	$227.7209	$227.72	$227.70	$227.70
Purchase #6	$175.76	13.403%	$199.3171	$199.32	$199.30	$199.30
Purchase #7	$149.62	3.134%	$154.3091	$154.31	$154.30	$154.30
7 purchase totals =	$716.42		$772.1319	$772.13	$772.10	$772.10