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	$69.85	11.513%	$77.8918	$77.89	$77.90	$77.90
Purchase #2	$34.55	8.397%	$37.4512	$37.45	$37.45	$37.50
Purchase #3	$43.56	11.798%	$48.6992	$48.70	$48.70	$48.70
Purchase #4	$63.25	6.529%	$67.3796	$67.38	$67.40	$67.40
Purchase #5	$220.65	5.488%	$232.7593	$232.76	$232.75	$232.80
Purchase #6	$35.57	6.534%	$37.8941	$37.89	$37.90	$37.90
Purchase #7	$208.26	13.564%	$236.5084	$236.51	$236.50	$236.50
7 purchase totals =	$675.69		$738.5836	$738.58	$738.60	$738.70