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 $155.26   4.509%   $162.2607   $162.26   $162.25   $162.30  
  Purchase #2 $216.54   13.462%   $245.6906   $245.69   $245.70   $245.70  
  Purchase #3 $104.29   10.587%   $115.3312   $115.33   $115.35   $115.30  
  Purchase #4 $201.93   5.311%   $212.6545   $212.65   $212.65   $212.70  
  Purchase #5 $167.80   4.249%   $174.9298   $174.93   $174.95   $174.90  
  Purchase #6 $41.71   8.532%   $45.2687   $45.27   $45.25   $45.30  
  Purchase #7 $46.99   10.657%   $51.9977   $52.00   $52.00   $52.00  
  7 purchase totals = $934.52       $1,008.1332   $1,008.13   $1,008.15   $1,008.20