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 $69.56   12.362%   $78.159   $78.16   $78.15   $78.20  
  Purchase #2 $181.79   8.188%   $196.675   $196.68   $196.70   $196.70  
  Purchase #3 $174.92   9.545%   $191.6161   $191.62   $191.60   $191.60  
  Purchase #4 $91.79   5.841%   $97.1515   $97.15   $97.15   $97.20  
  Purchase #5 $204.53   3.130%   $210.9318   $210.93   $210.95   $210.90  
  Purchase #6 $184.47   7.387%   $198.0968   $198.10   $198.10   $198.10  
  Purchase #7 $179.31   5.291%   $188.7973   $188.80   $188.80   $188.80  
  7 purchase totals = $1,086.37       $1,161.4275   $1,161.44   $1,161.45   $1,161.50