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	$134.95	8.700%	$146.6907	$146.69	$146.70	$146.70
Purchase #2	$94.26	6.491%	$100.3784	$100.38	$100.40	$100.40
Purchase #3	$51.63	13.568%	$58.6352	$58.64	$58.65	$58.60
Purchase #4	$223.78	3.459%	$231.5206	$231.52	$231.50	$231.50
Purchase #5	$29.43	7.388%	$31.6043	$31.60	$31.60	$31.60
Purchase #6	$201.39	5.512%	$212.4906	$212.49	$212.50	$212.50
Purchase #7	$137.90	11.603%	$153.9005	$153.90	$153.90	$153.90
7 purchase totals =	$873.34		$935.2203	$935.22	$935.25	$935.20