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	$229.61	13.373%	$260.3157	$260.32	$260.30	$260.30
Purchase #2	$78.71	13.260%	$89.1469	$89.15	$89.15	$89.10
Purchase #3	$35.31	3.275%	$36.4664	$36.47	$36.45	$36.50
Purchase #4	$133.30	13.684%	$151.5408	$151.54	$151.55	$151.50
Purchase #5	$13.35	4.632%	$13.9684	$13.97	$13.95	$14.00
Purchase #6	$186.53	3.335%	$192.7508	$192.75	$192.75	$192.80
Purchase #7	$192.78	5.533%	$203.4465	$203.45	$203.45	$203.40
7 purchase totals =	$869.59		$947.6355	$947.65	$947.60	$947.60