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	$169.90	10.468%	$187.6851	$187.69	$187.70	$187.70
Purchase #2	$140.61	8.490%	$152.5478	$152.55	$152.55	$152.50
Purchase #3	$121.56	4.452%	$126.9719	$126.97	$126.95	$127.00
Purchase #4	$191.32	9.189%	$208.9004	$208.90	$208.90	$208.90
Purchase #5	$40.31	6.435%	$42.9039	$42.90	$42.90	$42.90
Purchase #6	$104.64	5.667%	$110.5699	$110.57	$110.55	$110.60
Purchase #7	$34.37	9.853%	$37.7565	$37.76	$37.75	$37.80
7 purchase totals =	$802.71		$867.3355	$867.34	$867.30	$867.40