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 $69.47   12.616%   $78.2343   $78.23   $78.25   $78.20  
  Purchase #2 $244.64   5.426%   $257.9142   $257.91   $257.90   $257.90  
  Purchase #3 $121.39   10.151%   $133.7123   $133.71   $133.70   $133.70  
  Purchase #4 $169.25   4.264%   $176.4668   $176.47   $176.45   $176.50  
  Purchase #5 $192.90   4.366%   $201.322   $201.32   $201.30   $201.30  
  Purchase #6 $184.64   10.306%   $203.669   $203.67   $203.65   $203.70  
  Purchase #7 $92.61   4.762%   $97.0201   $97.02   $97.00   $97.00  
  7 purchase totals = $1,074.90       $1,148.3387   $1,148.33   $1,148.25   $1,148.30