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	$235.50	12.154%	$264.1227	$264.12	$264.10	$264.10
Purchase #2	$44.78	8.271%	$48.4838	$48.48	$48.50	$48.50
Purchase #3	$106.42	11.118%	$118.2518	$118.25	$118.25	$118.30
Purchase #4	$226.96	8.217%	$245.6093	$245.61	$245.60	$245.60
Purchase #5	$121.85	7.825%	$131.3848	$131.38	$131.40	$131.40
Purchase #6	$160.66	12.358%	$180.5144	$180.51	$180.50	$180.50
Purchase #7	$148.29	3.296%	$153.1776	$153.18	$153.20	$153.20
7 purchase totals =	$1,044.46		$1,141.5444	$1,141.53	$1,141.55	$1,141.60