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 $244.79   7.732%   $263.7172   $263.72   $263.70   $263.70  
  Purchase #2 $86.51   12.146%   $97.0175   $97.02   $97.00   $97.00  
  Purchase #3 $53.87   10.721%   $59.6454   $59.65   $59.65   $59.60  
  Purchase #4 $232.76   12.402%   $261.6269   $261.63   $261.65   $261.60  
  Purchase #5 $67.35   10.408%   $74.3598   $74.36   $74.35   $74.40  
  Purchase #6 $205.85   10.858%   $228.2012   $228.20   $228.20   $228.20  
  Purchase #7 $164.42   6.845%   $175.6745   $175.67   $175.65   $175.70  
  7 purchase totals = $1,055.55       $1,160.2425   $1,160.25   $1,160.20   $1,160.20