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 $187.34   8.212%   $202.7244   $202.72   $202.70   $202.70  
  Purchase #2 $206.76   10.261%   $227.9756   $227.98   $228.00   $228.00  
  Purchase #3 $70.50   4.785%   $73.8734   $73.87   $73.85   $73.90  
  Purchase #4 $102.34   6.538%   $109.031   $109.03   $109.05   $109.00  
  Purchase #5 $109.86   4.109%   $114.3741   $114.37   $114.35   $114.40  
  Purchase #6 $11.35   6.264%   $12.061   $12.06   $12.05   $12.10  
  Purchase #7 $249.40   10.153%   $274.7216   $274.72   $274.70   $274.70  
  7 purchase totals = $937.55       $1,014.7611   $1,014.75   $1,014.70   $1,014.80