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	$35.48	8.545%	$38.5118	$38.51	$38.50	$38.50
Purchase #2	$6.75	11.110%	$7.4999	$7.50	$7.50	$7.50
Purchase #3	$111.97	10.296%	$123.4984	$123.50	$123.50	$123.50
Purchase #4	$172.30	11.629%	$192.3368	$192.34	$192.35	$192.30
Purchase #5	$233.52	7.188%	$250.3054	$250.31	$250.30	$250.30
Purchase #6	$14.34	4.311%	$14.9582	$14.96	$14.95	$15.00
Purchase #7	$133.85	4.485%	$139.8532	$139.85	$139.85	$139.90
7 purchase totals =	$708.21		$766.9637	$766.97	$766.95	$767.00