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	$70.67	13.333%	$80.0924	$80.09	$80.10	$80.10
Purchase #2	$94.42	11.728%	$105.4936	$105.49	$105.50	$105.50
Purchase #3	$218.88	11.244%	$243.4909	$243.49	$243.50	$243.50
Purchase #4	$158.38	5.680%	$167.376	$167.38	$167.40	$167.40
Purchase #5	$231.29	12.797%	$260.8882	$260.89	$260.90	$260.90
Purchase #6	$35.67	13.448%	$40.4669	$40.47	$40.45	$40.50
Purchase #7	$148.73	5.557%	$156.9949	$156.99	$157.00	$157.00
7 purchase totals =	$958.04		$1,054.8029	$1,054.80	$1,054.85	$1,054.90