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	$95.54	8.656%	$103.8099	$103.81	$103.80	$103.80
Purchase #2	$100.61	8.352%	$109.0129	$109.01	$109.00	$109.00
Purchase #3	$103.82	13.828%	$118.1762	$118.18	$118.20	$118.20
Purchase #4	$147.62	3.440%	$152.6981	$152.70	$152.70	$152.70
Purchase #5	$14.33	3.820%	$14.8774	$14.88	$14.90	$14.90
Purchase #6	$188.66	10.707%	$208.8598	$208.86	$208.85	$208.90
Purchase #7	$105.57	11.268%	$117.4656	$117.47	$117.45	$117.50
7 purchase totals =	$756.15		$824.8999	$824.91	$824.90	$825.00