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 $134.74   8.535%   $146.2401   $146.24   $146.25   $146.20  
  Purchase #2 $145.42   6.332%   $154.628   $154.63   $154.65   $154.60  
  Purchase #3 $37.68   9.607%   $41.2999   $41.30   $41.30   $41.30  
  Purchase #4 $179.77   12.757%   $202.7033   $202.70   $202.70   $202.70  
  Purchase #5 $199.96   6.869%   $213.6953   $213.70   $213.70   $213.70  
  Purchase #6 $187.31   10.495%   $206.9682   $206.97   $206.95   $207.00  
  Purchase #7 $202.87   12.204%   $227.6283   $227.63   $227.65   $227.60  
  7 purchase totals = $1,087.75       $1,193.1631   $1,193.17   $1,193.20   $1,193.10