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	$131.48	11.331%	$146.378	$146.38	$146.40	$146.40
Purchase #2	$40.90	6.705%	$43.6423	$43.64	$43.65	$43.60
Purchase #3	$222.39	13.526%	$252.4705	$252.47	$252.45	$252.50
Purchase #4	$40.93	7.569%	$44.028	$44.03	$44.05	$44.00
Purchase #5	$46.96	13.785%	$53.4334	$53.43	$53.45	$53.40
Purchase #6	$88.96	6.711%	$94.9301	$94.93	$94.95	$94.90
Purchase #7	$250.42	9.275%	$273.6465	$273.65	$273.65	$273.60
7 purchase totals =	$822.04		$908.5288	$908.53	$908.60	$908.40