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	$172.38	7.330%	$185.0155	$185.02	$185.00	$185.00
Purchase #2	$73.56	13.564%	$83.5377	$83.54	$83.55	$83.50
Purchase #3	$108.81	10.199%	$119.9075	$119.91	$119.90	$119.90
Purchase #4	$232.43	10.361%	$256.5121	$256.51	$256.50	$256.50
Purchase #5	$13.60	9.533%	$14.8965	$14.90	$14.90	$14.90
Purchase #6	$133.28	5.406%	$140.4851	$140.49	$140.50	$140.50
Purchase #7	$75.55	12.748%	$85.1811	$85.18	$85.20	$85.20
7 purchase totals =	$809.61		$885.5355	$885.55	$885.55	$885.50