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	$217.30	4.691%	$227.4935	$227.49	$227.50	$227.50
Purchase #2	$34.53	9.635%	$37.857	$37.86	$37.85	$37.90
Purchase #3	$31.50	12.828%	$35.5408	$35.54	$35.55	$35.50
Purchase #4	$86.96	6.637%	$92.7315	$92.73	$92.75	$92.70
Purchase #5	$122.96	13.774%	$139.8965	$139.90	$139.90	$139.90
Purchase #6	$192.27	13.267%	$217.7785	$217.78	$217.80	$217.80
Purchase #7	$198.59	11.838%	$222.0991	$222.10	$222.10	$222.10
7 purchase totals =	$884.11		$973.3969	$973.40	$973.45	$973.40