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	$103.39	6.259%	$109.8612	$109.86	$109.85	$109.90
Purchase #2	$68.27	5.329%	$71.9081	$71.91	$71.90	$71.90
Purchase #3	$37.89	3.584%	$39.248	$39.25	$39.25	$39.20
Purchase #4	$82.77	6.243%	$87.9373	$87.94	$87.95	$87.90
Purchase #5	$147.26	11.868%	$164.7368	$164.74	$164.75	$164.70
Purchase #6	$113.83	9.423%	$124.5562	$124.56	$124.55	$124.60
Purchase #7	$14.25	10.395%	$15.7313	$15.73	$15.75	$15.70
7 purchase totals =	$567.66		$613.9789	$613.99	$614.00	$613.90