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 $83.57   13.690%   $95.0107   $95.01   $95.00   $95.00  
  Purchase #2 $183.92   10.189%   $202.6596   $202.66   $202.65   $202.70  
  Purchase #3 $246.37   7.376%   $264.5423   $264.54   $264.55   $264.50  
  Purchase #4 $51.64   12.236%   $57.9587   $57.96   $57.95   $58.00  
  Purchase #5 $92.72   10.368%   $102.3332   $102.33   $102.35   $102.30  
  Purchase #6 $163.83   8.748%   $178.1618   $178.16   $178.15   $178.20  
  Purchase #7 $222.53   7.868%   $240.0387   $240.04   $240.05   $240.00  
  7 purchase totals = $1,044.58       $1,140.7050   $1,140.70   $1,140.70   $1,140.70