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	$160.39	4.341%	$167.3525	$167.35	$167.35	$167.40
Purchase #2	$15.59	5.709%	$16.48	$16.48	$16.50	$16.50
Purchase #3	$157.49	5.624%	$166.3472	$166.35	$166.35	$166.30
Purchase #4	$79.73	4.149%	$83.038	$83.04	$83.05	$83.00
Purchase #5	$184.38	8.715%	$200.4487	$200.45	$200.45	$200.40
Purchase #6	$60.30	12.594%	$67.8942	$67.89	$67.90	$67.90
Purchase #7	$108.59	11.398%	$120.9671	$120.97	$120.95	$121.00
7 purchase totals =	$766.47		$822.5277	$822.53	$822.55	$822.50