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	$107.25	10.807%	$118.8405	$118.84	$118.85	$118.80
Purchase #2	$92.44	11.572%	$103.1372	$103.14	$103.15	$103.10
Purchase #3	$230.68	5.579%	$243.5496	$243.55	$243.55	$243.50
Purchase #4	$170.88	11.734%	$190.9311	$190.93	$190.95	$190.90
Purchase #5	$102.56	10.729%	$113.5637	$113.56	$113.55	$113.60
Purchase #6	$130.31	6.858%	$139.2467	$139.25	$139.25	$139.20
Purchase #7	$102.85	12.798%	$116.0127	$116.01	$116.00	$116.00
7 purchase totals =	$936.97		$1,025.2815	$1,025.28	$1,025.30	$1,025.10