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 $223.59   6.293%   $237.6605   $237.66   $237.65   $237.70  
  Purchase #2 $200.73   11.842%   $224.5004   $224.50   $224.50   $224.50  
  Purchase #3 $179.35   7.345%   $192.5233   $192.52   $192.50   $192.50  
  Purchase #4 $245.87   6.210%   $261.1385   $261.14   $261.15   $261.10  
  Purchase #5 $59.80   10.503%   $66.0808   $66.08   $66.10   $66.10  
  Purchase #6 $213.97   3.803%   $222.1073   $222.11   $222.10   $222.10  
  Purchase #7 $236.26   10.383%   $260.7909   $260.79   $260.80   $260.80  
  7 purchase totals = $1,359.57       $1,464.8017   $1,464.80   $1,464.80   $1,464.80