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	$242.25	9.339%	$264.8737	$264.87	$264.85	$264.90
Purchase #2	$39.71	4.170%	$41.3659	$41.37	$41.35	$41.40
Purchase #3	$195.56	11.869%	$218.771	$218.77	$218.75	$218.80
Purchase #4	$227.50	4.853%	$238.5406	$238.54	$238.55	$238.50
Purchase #5	$15.69	11.232%	$17.4523	$17.45	$17.45	$17.50
Purchase #6	$42.98	13.758%	$48.8932	$48.89	$48.90	$48.90
Purchase #7	$32.77	5.113%	$34.4455	$34.45	$34.45	$34.40
7 purchase totals =	$796.46		$864.3422	$864.34	$864.30	$864.40