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	$94.62	12.286%	$106.245	$106.25	$106.25	$106.20
Purchase #2	$242.89	12.765%	$273.8949	$273.89	$273.90	$273.90
Purchase #3	$241.66	8.603%	$262.45	$262.45	$262.45	$262.50
Purchase #4	$33.27	5.410%	$35.0699	$35.07	$35.05	$35.10
Purchase #5	$239.73	8.290%	$259.6036	$259.60	$259.60	$259.60
Purchase #6	$143.34	9.579%	$157.0705	$157.07	$157.05	$157.10
Purchase #7	$34.27	9.765%	$37.6165	$37.62	$37.60	$37.60
7 purchase totals =	$1,029.78		$1,131.9504	$1,131.95	$1,131.90	$1,132.00