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	$35.69	6.688%	$38.0769	$38.08	$38.10	$38.10
Purchase #2	$92.36	6.304%	$98.1824	$98.18	$98.20	$98.20
Purchase #3	$244.33	9.617%	$267.8272	$267.83	$267.85	$267.80
Purchase #4	$119.60	12.311%	$134.324	$134.32	$134.30	$134.30
Purchase #5	$80.50	6.309%	$85.5787	$85.58	$85.60	$85.60
Purchase #6	$222.56	8.358%	$241.1616	$241.16	$241.15	$241.20
Purchase #7	$162.90	6.154%	$172.9249	$172.92	$172.90	$172.90
7 purchase totals =	$957.94		$1,038.0757	$1,038.07	$1,038.10	$1,038.10