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 $207.65   12.547%   $233.7038   $233.70   $233.70   $233.70  
  Purchase #2 $40.69   3.340%   $42.049   $42.05   $42.05   $42.00  
  Purchase #3 $223.75   4.599%   $234.0403   $234.04   $234.05   $234.00  
  Purchase #4 $163.72   6.700%   $174.6892   $174.69   $174.70   $174.70  
  Purchase #5 $95.95   12.316%   $107.7672   $107.77   $107.75   $107.80  
  Purchase #6 $102.45   7.763%   $110.4032   $110.40   $110.40   $110.40  
  Purchase #7 $241.31   3.418%   $249.558   $249.56   $249.55   $249.60  
  7 purchase totals = $1,075.52       $1,152.2107   $1,152.21   $1,152.20   $1,152.20