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 $178.96   10.611%   $197.9494   $197.95   $197.95   $197.90  
  Purchase #2 $20.27   11.484%   $22.5978   $22.60   $22.60   $22.60  
  Purchase #3 $84.26   10.713%   $93.2868   $93.29   $93.30   $93.30  
  Purchase #4 $57.55   3.488%   $59.5573   $59.56   $59.55   $59.60  
  Purchase #5 $50.63   10.555%   $55.974   $55.97   $55.95   $56.00  
  Purchase #6 $31.47   8.577%   $34.1692   $34.17   $34.15   $34.20  
  Purchase #7 $231.87   12.244%   $260.2602   $260.26   $260.25   $260.30  
  7 purchase totals = $655.01       $723.7947   $723.80   $723.75   $723.90