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 $84.76   13.130%   $95.889   $95.89   $95.90   $95.90  
  Purchase #2 $233.94   6.704%   $249.6233   $249.62   $249.60   $249.60  
  Purchase #3 $77.73   7.296%   $83.4012   $83.40   $83.40   $83.40  
  Purchase #4 $165.26   6.358%   $175.7672   $175.77   $175.75   $175.80  
  Purchase #5 $187.56   9.203%   $204.8211   $204.82   $204.80   $204.80  
  Purchase #6 $220.37   4.628%   $230.5687   $230.57   $230.55   $230.60  
  Purchase #7 $23.25   10.720%   $25.7424   $25.74   $25.75   $25.70  
  7 purchase totals = $992.87       $1,065.8129   $1,065.81   $1,065.75   $1,065.80