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	$43.99	5.621%	$46.4627	$46.46	$46.45	$46.50
Purchase #2	$120.86	13.485%	$137.158	$137.16	$137.15	$137.20
Purchase #3	$78.57	13.196%	$88.9381	$88.94	$88.95	$88.90
Purchase #4	$147.66	13.588%	$167.724	$167.72	$167.70	$167.70
Purchase #5	$55.81	7.210%	$59.8339	$59.83	$59.85	$59.80
Purchase #6	$23.34	6.155%	$24.7766	$24.78	$24.80	$24.80
Purchase #7	$143.82	8.611%	$156.2043	$156.20	$156.20	$156.20
7 purchase totals =	$614.05		$681.0976	$681.09	$681.10	$681.10