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	$168.92	9.379%	$184.763	$184.76	$184.75	$184.80
Purchase #2	$216.47	10.277%	$238.7166	$238.72	$238.70	$238.70
Purchase #3	$129.57	11.467%	$144.4278	$144.43	$144.45	$144.40
Purchase #4	$147.76	11.540%	$164.8115	$164.81	$164.80	$164.80
Purchase #5	$71.69	5.217%	$75.4301	$75.43	$75.45	$75.40
Purchase #6	$204.82	8.751%	$222.7438	$222.74	$222.75	$222.70
Purchase #7	$109.83	12.526%	$123.5873	$123.59	$123.60	$123.60
7 purchase totals =	$1,049.06		$1,154.4801	$1,154.48	$1,154.50	$1,154.40