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	$79.91	7.249%	$85.7027	$85.70	$85.70	$85.70
Purchase #2	$151.79	6.779%	$162.0798	$162.08	$162.10	$162.10
Purchase #3	$145.93	11.619%	$162.8856	$162.89	$162.90	$162.90
Purchase #4	$83.27	4.757%	$87.2312	$87.23	$87.25	$87.20
Purchase #5	$152.53	9.148%	$166.4834	$166.48	$166.50	$166.50
Purchase #6	$158.61	11.443%	$176.7597	$176.76	$176.75	$176.80
Purchase #7	$109.89	3.460%	$113.6922	$113.69	$113.70	$113.70
7 purchase totals =	$881.93		$954.8346	$954.83	$954.90	$954.90