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 $42.66   7.487%   $45.854   $45.85   $45.85   $45.90  
  Purchase #2 $118.93   8.753%   $129.3399   $129.34   $129.35   $129.30  
  Purchase #3 $205.81   9.284%   $224.9174   $224.92   $224.90   $224.90  
  Purchase #4 $107.73   5.317%   $113.458   $113.46   $113.45   $113.50  
  Purchase #5 $19.36   5.798%   $20.4825   $20.48   $20.50   $20.50  
  Purchase #6 $82.41   13.649%   $93.6581   $93.66   $93.65   $93.70  
  Purchase #7 $148.64   6.203%   $157.8601   $157.86   $157.85   $157.90  
  7 purchase totals = $725.54       $785.5700   $785.57   $785.55   $785.70