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	$112.51	9.555%	$123.2603	$123.26	$123.25	$123.30
Purchase #2	$77.52	9.795%	$85.1131	$85.11	$85.10	$85.10
Purchase #3	$188.41	3.783%	$195.5376	$195.54	$195.55	$195.50
Purchase #4	$94.46	7.725%	$101.757	$101.76	$101.75	$101.80
Purchase #5	$133.78	8.254%	$144.8222	$144.82	$144.80	$144.80
Purchase #6	$16.33	5.280%	$17.1922	$17.19	$17.20	$17.20
Purchase #7	$150.67	5.382%	$158.7791	$158.78	$158.80	$158.80
7 purchase totals =	$773.68		$826.4615	$826.46	$826.45	$826.50