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	$153.89	9.659%	$168.7542	$168.75	$168.75	$168.80
Purchase #2	$107.87	6.132%	$114.4846	$114.48	$114.50	$114.50
Purchase #3	$34.63	3.761%	$35.9324	$35.93	$35.95	$35.90
Purchase #4	$95.60	13.829%	$108.8205	$108.82	$108.80	$108.80
Purchase #5	$114.95	7.743%	$123.8506	$123.85	$123.85	$123.90
Purchase #6	$36.89	3.434%	$38.1568	$38.16	$38.15	$38.20
Purchase #7	$185.34	7.609%	$199.4425	$199.44	$199.45	$199.40
7 purchase totals =	$729.17		$789.4416	$789.43	$789.45	$789.50