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	$82.77	10.544%	$91.4973	$91.50	$91.50	$91.50
Purchase #2	$82.93	10.791%	$91.879	$91.88	$91.90	$91.90
Purchase #3	$22.77	7.412%	$24.4577	$24.46	$24.45	$24.50
Purchase #4	$29.61	10.796%	$32.8067	$32.81	$32.80	$32.80
Purchase #5	$245.95	13.175%	$278.3539	$278.35	$278.35	$278.40
Purchase #6	$159.56	7.810%	$172.0216	$172.02	$172.00	$172.00
Purchase #7	$90.47	5.226%	$95.198	$95.20	$95.20	$95.20
7 purchase totals =	$714.06		$786.2142	$786.22	$786.20	$786.30