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	$119.36	6.747%	$127.4132	$127.41	$127.40	$127.40
Purchase #2	$123.27	12.480%	$138.6541	$138.65	$138.65	$138.70
Purchase #3	$68.89	12.553%	$77.5378	$77.54	$77.55	$77.50
Purchase #4	$213.98	4.447%	$223.4957	$223.50	$223.50	$223.50
Purchase #5	$121.92	9.405%	$133.3866	$133.39	$133.40	$133.40
Purchase #6	$109.78	7.257%	$117.7467	$117.75	$117.75	$117.70
Purchase #7	$82.38	9.828%	$90.4763	$90.48	$90.50	$90.50
7 purchase totals =	$839.58		$908.7104	$908.72	$908.75	$908.70