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	$113.94	3.625%	$118.0703	$118.07	$118.05	$118.10
Purchase #2	$79.28	8.708%	$86.1837	$86.18	$86.20	$86.20
Purchase #3	$102.63	10.416%	$113.3199	$113.32	$113.30	$113.30
Purchase #4	$84.57	6.579%	$90.1339	$90.13	$90.15	$90.10
Purchase #5	$89.67	6.862%	$95.8232	$95.82	$95.80	$95.80
Purchase #6	$81.86	5.539%	$86.3942	$86.39	$86.40	$86.40
Purchase #7	$67.85	6.217%	$72.0682	$72.07	$72.05	$72.10
7 purchase totals =	$619.80		$661.9934	$661.98	$661.95	$662.00