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 $87.66   8.442%   $95.0603   $95.06   $95.05   $95.10  
  Purchase #2 $167.75   12.152%   $188.135   $188.14   $188.15   $188.10  
  Purchase #3 $104.26   7.304%   $111.8752   $111.88   $111.90   $111.90  
  Purchase #4 $202.83   5.614%   $214.2169   $214.22   $214.20   $214.20  
  Purchase #5 $232.82   5.533%   $245.7019   $245.70   $245.70   $245.70  
  Purchase #6 $94.75   13.141%   $107.2011   $107.20   $107.20   $107.20  
  Purchase #7 $31.43   13.272%   $35.6014   $35.60   $35.60   $35.60  
  7 purchase totals = $921.50       $997.7918   $997.80   $997.80   $997.80