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	$118.61	7.415%	$127.4049	$127.40	$127.40	$127.40
Purchase #2	$186.78	11.561%	$208.3736	$208.37	$208.35	$208.40
Purchase #3	$52.43	10.414%	$57.8901	$57.89	$57.90	$57.90
Purchase #4	$48.82	5.450%	$51.4807	$51.48	$51.50	$51.50
Purchase #5	$22.45	5.167%	$23.61	$23.61	$23.60	$23.60
Purchase #6	$215.96	6.156%	$229.2545	$229.25	$229.25	$229.30
Purchase #7	$152.69	5.669%	$161.346	$161.35	$161.35	$161.30
7 purchase totals =	$797.74		$859.3598	$859.35	$859.35	$859.40