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	$109.72	8.357%	$118.8893	$118.89	$118.90	$118.90
Purchase #2	$166.67	3.249%	$172.0851	$172.09	$172.10	$172.10
Purchase #3	$99.32	3.647%	$102.9422	$102.94	$102.95	$102.90
Purchase #4	$109.88	10.417%	$121.3262	$121.33	$121.35	$121.30
Purchase #5	$41.77	7.846%	$45.0473	$45.05	$45.05	$45.00
Purchase #6	$107.97	5.391%	$113.7907	$113.79	$113.80	$113.80
Purchase #7	$89.45	3.411%	$92.5011	$92.50	$92.50	$92.50
7 purchase totals =	$724.78		$766.5819	$766.59	$766.65	$766.50