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 $119.59   4.505%   $124.9775   $124.98   $125.00   $125.00  
  Purchase #2 $8.69   5.131%   $9.1359   $9.14   $9.15   $9.10  
  Purchase #3 $15.34   5.369%   $16.1636   $16.16   $16.15   $16.20  
  Purchase #4 $162.89   5.431%   $171.7366   $171.74   $171.75   $171.70  
  Purchase #5 $187.93   11.264%   $209.0984   $209.10   $209.10   $209.10  
  Purchase #6 $233.64   11.154%   $259.7002   $259.70   $259.70   $259.70  
  Purchase #7 $138.36   4.494%   $144.5779   $144.58   $144.60   $144.60  
  7 purchase totals = $866.44       $935.3901   $935.40   $935.45   $935.40