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 $89.26   6.402%   $94.9744   $94.97   $94.95   $95.00  
  Purchase #2 $247.90   7.602%   $266.7454   $266.75   $266.75   $266.70  
  Purchase #3 $125.30   13.839%   $142.6403   $142.64   $142.65   $142.60  
  Purchase #4 $190.27   13.475%   $215.9089   $215.91   $215.90   $215.90  
  Purchase #5 $16.26   8.262%   $17.6034   $17.60   $17.60   $17.60  
  Purchase #6 $155.79   6.404%   $165.7668   $165.77   $165.75   $165.80  
  Purchase #7 $60.97   10.833%   $67.5749   $67.57   $67.55   $67.60  
  7 purchase totals = $885.75       $971.2141   $971.21   $971.15   $971.20