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	$110.96	11.300%	$123.4985	$123.50	$123.50	$123.50
Purchase #2	$37.80	5.391%	$39.8378	$39.84	$39.85	$39.80
Purchase #3	$153.29	9.332%	$167.595	$167.60	$167.60	$167.60
Purchase #4	$29.83	7.603%	$32.098	$32.10	$32.10	$32.10
Purchase #5	$147.63	13.507%	$167.5704	$167.57	$167.55	$167.60
Purchase #6	$30.91	6.520%	$32.9253	$32.93	$32.95	$32.90
Purchase #7	$205.80	10.534%	$227.479	$227.48	$227.50	$227.50
7 purchase totals =	$716.22		$791.0040	$791.02	$791.05	$791.00