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	$111.27	5.731%	$117.6469	$117.65	$117.65	$117.60
Purchase #2	$206.56	5.621%	$218.1707	$218.17	$218.15	$218.20
Purchase #3	$118.28	13.108%	$133.7841	$133.78	$133.80	$133.80
Purchase #4	$208.65	8.282%	$225.9304	$225.93	$225.95	$225.90
Purchase #5	$51.90	13.868%	$59.0975	$59.10	$59.10	$59.10
Purchase #6	$212.32	12.460%	$238.7751	$238.78	$238.80	$238.80
Purchase #7	$8.96	13.516%	$10.171	$10.17	$10.15	$10.20
7 purchase totals =	$917.94		$1,003.5757	$1,003.58	$1,003.60	$1,003.60