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	$250.71	4.339%	$261.5883	$261.59	$261.60	$261.60
Purchase #2	$49.91	5.652%	$52.7309	$52.73	$52.75	$52.70
Purchase #3	$43.77	3.523%	$45.312	$45.31	$45.30	$45.30
Purchase #4	$40.29	4.316%	$42.0289	$42.03	$42.05	$42.00
Purchase #5	$231.84	13.369%	$262.8347	$262.83	$262.85	$262.80
Purchase #6	$79.31	7.703%	$85.4192	$85.42	$85.40	$85.40
Purchase #7	$82.97	4.800%	$86.9526	$86.95	$86.95	$87.00
7 purchase totals =	$778.80		$836.8666	$836.86	$836.90	$836.80