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	$103.52	9.495%	$113.3492	$113.35	$113.35	$113.30
Purchase #2	$9.49	11.853%	$10.6148	$10.61	$10.60	$10.60
Purchase #3	$156.73	11.343%	$174.5079	$174.51	$174.50	$174.50
Purchase #4	$20.73	11.770%	$23.1699	$23.17	$23.15	$23.20
Purchase #5	$66.80	8.625%	$72.5615	$72.56	$72.55	$72.60
Purchase #6	$65.54	10.695%	$72.5495	$72.55	$72.55	$72.50
Purchase #7	$45.85	8.535%	$49.7633	$49.76	$49.75	$49.80
7 purchase totals =	$468.66		$516.5161	$516.51	$516.45	$516.50