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	$173.80	11.546%	$193.8669	$193.87	$193.85	$193.90
Purchase #2	$59.26	10.686%	$65.5925	$65.59	$65.60	$65.60
Purchase #3	$141.85	13.320%	$160.7444	$160.74	$160.75	$160.70
Purchase #4	$82.58	7.314%	$88.6199	$88.62	$88.60	$88.60
Purchase #5	$50.59	11.510%	$56.4129	$56.41	$56.40	$56.40
Purchase #6	$188.78	5.855%	$199.8331	$199.83	$199.85	$199.80
Purchase #7	$155.27	7.845%	$167.4509	$167.45	$167.45	$167.50
7 purchase totals =	$852.13		$932.5206	$932.51	$932.50	$932.50