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	$138.77	9.803%	$152.3736	$152.37	$152.35	$152.40
Purchase #2	$167.50	11.292%	$186.4141	$186.41	$186.40	$186.40
Purchase #3	$31.92	6.178%	$33.892	$33.89	$33.90	$33.90
Purchase #4	$209.69	12.712%	$236.3458	$236.35	$236.35	$236.30
Purchase #5	$164.40	11.266%	$182.9213	$182.92	$182.90	$182.90
Purchase #6	$77.38	10.496%	$85.5018	$85.50	$85.50	$85.50
Purchase #7	$81.26	11.179%	$90.3441	$90.34	$90.35	$90.30
7 purchase totals =	$870.92		$967.7927	$967.78	$967.75	$967.70