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	$40.55	5.340%	$42.7154	$42.72	$42.70	$42.70
Purchase #2	$227.63	7.301%	$244.2493	$244.25	$244.25	$244.20
Purchase #3	$125.27	6.205%	$133.043	$133.04	$133.05	$133.00
Purchase #4	$61.69	3.142%	$63.6283	$63.63	$63.65	$63.60
Purchase #5	$37.42	13.704%	$42.548	$42.55	$42.55	$42.50
Purchase #6	$227.59	12.672%	$256.4302	$256.43	$256.45	$256.40
Purchase #7	$218.70	5.744%	$231.2621	$231.26	$231.25	$231.30
7 purchase totals =	$938.85		$1,013.8763	$1,013.88	$1,013.90	$1,013.70