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 $65.79   9.419%   $71.9868   $71.99   $72.00   $72.00  
  Purchase #2 $74.36   10.763%   $82.3634   $82.36   $82.35   $82.40  
  Purchase #3 $195.25   7.600%   $210.089   $210.09   $210.10   $210.10  
  Purchase #4 $229.28   13.862%   $261.0628   $261.06   $261.05   $261.10  
  Purchase #5 $15.70   9.125%   $17.1326   $17.13   $17.15   $17.10  
  Purchase #6 $172.99   12.721%   $194.9961   $195.00   $195.00   $195.00  
  Purchase #7 $196.52   8.246%   $212.725   $212.73   $212.75   $212.70  
  7 purchase totals = $949.89       $1,050.3557   $1,050.36   $1,050.40   $1,050.40