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 $162.76   8.524%   $176.6337   $176.63   $176.65   $176.60  
  Purchase #2 $173.43   4.476%   $181.1927   $181.19   $181.20   $181.20  
  Purchase #3 $46.71   7.433%   $50.182   $50.18   $50.20   $50.20  
  Purchase #4 $218.98   7.868%   $236.2093   $236.21   $236.20   $236.20  
  Purchase #5 $53.53   8.255%   $57.9489   $57.95   $57.95   $57.90  
  Purchase #6 $186.49   8.630%   $202.5841   $202.58   $202.60   $202.60  
  Purchase #7 $42.50   3.844%   $44.1337   $44.13   $44.15   $44.10  
  7 purchase totals = $884.40       $948.8844   $948.87   $948.95   $948.80