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	$66.96	8.624%	$72.7346	$72.73	$72.75	$72.70
Purchase #2	$118.80	7.812%	$128.0807	$128.08	$128.10	$128.10
Purchase #3	$122.36	9.119%	$133.518	$133.52	$133.50	$133.50
Purchase #4	$94.56	6.187%	$100.4104	$100.41	$100.40	$100.40
Purchase #5	$222.72	10.847%	$246.8784	$246.88	$246.90	$246.90
Purchase #6	$149.88	12.390%	$168.4501	$168.45	$168.45	$168.50
Purchase #7	$84.65	3.754%	$87.8278	$87.83	$87.85	$87.80
7 purchase totals =	$859.93		$937.9000	$937.90	$937.95	$937.90