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	$207.61	7.720%	$223.6375	$223.64	$223.65	$223.60
Purchase #2	$50.69	13.610%	$57.5889	$57.59	$57.60	$57.60
Purchase #3	$167.93	7.211%	$180.0394	$180.04	$180.05	$180.00
Purchase #4	$159.77	3.610%	$165.5377	$165.54	$165.55	$165.50
Purchase #5	$23.26	4.582%	$24.3258	$24.33	$24.35	$24.30
Purchase #6	$107.27	4.800%	$112.419	$112.42	$112.40	$112.40
Purchase #7	$96.58	3.658%	$100.1129	$100.11	$100.10	$100.10
7 purchase totals =	$813.11		$863.6612	$863.67	$863.70	$863.50