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	$230.99	13.674%	$262.5756	$262.58	$262.60	$262.60
Purchase #2	$69.72	12.477%	$78.419	$78.42	$78.40	$78.40
Purchase #3	$57.41	3.516%	$59.4285	$59.43	$59.45	$59.40
Purchase #4	$14.91	10.505%	$16.4763	$16.48	$16.50	$16.50
Purchase #5	$100.69	11.466%	$112.2351	$112.24	$112.25	$112.20
Purchase #6	$81.33	3.842%	$84.4547	$84.45	$84.45	$84.50
Purchase #7	$131.56	7.634%	$141.6033	$141.60	$141.60	$141.60
7 purchase totals =	$686.61		$755.1925	$755.20	$755.25	$755.20