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	$54.88	12.537%	$61.7603	$61.76	$61.75	$61.80
Purchase #2	$221.54	4.460%	$231.4207	$231.42	$231.40	$231.40
Purchase #3	$82.31	3.782%	$85.423	$85.42	$85.40	$85.40
Purchase #4	$29.82	8.306%	$32.2968	$32.30	$32.30	$32.30
Purchase #5	$72.56	11.714%	$81.0597	$81.06	$81.05	$81.10
Purchase #6	$34.79	8.657%	$37.8018	$37.80	$37.80	$37.80
Purchase #7	$141.67	8.617%	$153.8777	$153.88	$153.90	$153.90
7 purchase totals =	$637.57		$683.6400	$683.64	$683.60	$683.70