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 $67.48   10.407%   $74.5026   $74.50   $74.50   $74.50  
  Purchase #2 $218.58   6.468%   $232.7178   $232.72   $232.70   $232.70  
  Purchase #3 $145.56   8.653%   $158.1553   $158.16   $158.15   $158.20  
  Purchase #4 $50.87   8.440%   $55.1634   $55.16   $55.15   $55.20  
  Purchase #5 $81.53   7.565%   $87.6977   $87.70   $87.70   $87.70  
  Purchase #6 $228.28   4.234%   $237.9454   $237.95   $237.95   $237.90  
  Purchase #7 $231.49   8.137%   $250.3263   $250.33   $250.35   $250.30  
  7 purchase totals = $1,023.79       $1,096.5085   $1,096.52   $1,096.50   $1,096.50