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	$132.70	6.427%	$141.2286	$141.23	$141.25	$141.20
Purchase #2	$15.81	4.184%	$16.4715	$16.47	$16.45	$16.50
Purchase #3	$53.93	11.151%	$59.9437	$59.94	$59.95	$59.90
Purchase #4	$190.27	13.186%	$215.359	$215.36	$215.35	$215.40
Purchase #5	$73.38	7.375%	$78.7918	$78.79	$78.80	$78.80
Purchase #6	$169.89	9.319%	$185.722	$185.72	$185.70	$185.70
Purchase #7	$21.92	9.528%	$24.0085	$24.01	$24.00	$24.00
7 purchase totals =	$657.90		$721.5251	$721.52	$721.50	$721.50