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	$121.64	3.460%	$125.8487	$125.85	$125.85	$125.80
Purchase #2	$133.59	5.804%	$141.3436	$141.34	$141.35	$141.30
Purchase #3	$83.47	10.788%	$92.4747	$92.47	$92.45	$92.50
Purchase #4	$118.80	12.351%	$133.473	$133.47	$133.45	$133.50
Purchase #5	$101.59	3.589%	$105.2361	$105.24	$105.25	$105.20
Purchase #6	$155.66	9.151%	$169.9044	$169.90	$169.90	$169.90
Purchase #7	$81.38	5.271%	$85.6695	$85.67	$85.65	$85.70
7 purchase totals =	$796.13		$853.9500	$853.94	$853.90	$853.90