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	$35.46	3.793%	$36.805	$36.81	$36.80	$36.80
Purchase #2	$111.48	4.248%	$116.2157	$116.22	$116.20	$116.20
Purchase #3	$153.78	12.439%	$172.9087	$172.91	$172.90	$172.90
Purchase #4	$43.79	4.298%	$45.6721	$45.67	$45.65	$45.70
Purchase #5	$239.38	4.121%	$249.2448	$249.24	$249.25	$249.20
Purchase #6	$64.51	3.869%	$67.0059	$67.01	$67.00	$67.00
Purchase #7	$250.26	4.724%	$262.0823	$262.08	$262.10	$262.10
7 purchase totals =	$898.66		$949.9345	$949.94	$949.90	$949.90