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	$106.95	4.279%	$111.5264	$111.53	$111.55	$111.50
Purchase #2	$221.63	9.662%	$243.0439	$243.04	$243.05	$243.00
Purchase #3	$246.64	7.688%	$265.6017	$265.60	$265.60	$265.60
Purchase #4	$30.34	7.431%	$32.5946	$32.59	$32.60	$32.60
Purchase #5	$24.90	10.481%	$27.5098	$27.51	$27.50	$27.50
Purchase #6	$178.35	10.806%	$197.6225	$197.62	$197.60	$197.60
Purchase #7	$35.80	11.248%	$39.8268	$39.83	$39.85	$39.80
7 purchase totals =	$844.61		$917.7257	$917.72	$917.75	$917.60