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	$101.59	11.544%	$113.3175	$113.32	$113.30	$113.30
Purchase #2	$69.52	8.646%	$75.5307	$75.53	$75.55	$75.50
Purchase #3	$51.55	7.112%	$55.2162	$55.22	$55.20	$55.20
Purchase #4	$90.88	7.575%	$97.7642	$97.76	$97.75	$97.80
Purchase #5	$102.66	9.554%	$112.4681	$112.47	$112.45	$112.50
Purchase #6	$82.62	9.284%	$90.2904	$90.29	$90.30	$90.30
Purchase #7	$246.41	4.243%	$256.8652	$256.87	$256.85	$256.90
7 purchase totals =	$745.23		$801.4523	$801.46	$801.40	$801.50