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	$40.67	10.723%	$45.031	$45.03	$45.05	$45.00
Purchase #2	$31.36	13.531%	$35.6033	$35.60	$35.60	$35.60
Purchase #3	$94.88	10.497%	$104.8396	$104.84	$104.85	$104.80
Purchase #4	$198.45	13.213%	$224.6712	$224.67	$224.65	$224.70
Purchase #5	$57.53	8.605%	$62.4805	$62.48	$62.50	$62.50
Purchase #6	$79.86	6.448%	$85.0094	$85.01	$85.00	$85.00
Purchase #7	$82.53	4.722%	$86.4271	$86.43	$86.45	$86.40
7 purchase totals =	$585.28		$644.0621	$644.06	$644.10	$644.00