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 $176.95   10.862%   $196.1703   $196.17   $196.15   $196.20  
  Purchase #2 $98.64   3.661%   $102.2512   $102.25   $102.25   $102.30  
  Purchase #3 $213.70   10.417%   $235.9611   $235.96   $235.95   $236.00  
  Purchase #4 $209.59   11.754%   $234.2252   $234.23   $234.25   $234.20  
  Purchase #5 $217.70   8.486%   $236.174   $236.17   $236.15   $236.20  
  Purchase #6 $181.60   5.701%   $191.953   $191.95   $191.95   $192.00  
  Purchase #7 $148.43   8.814%   $161.5126   $161.51   $161.50   $161.50  
  7 purchase totals = $1,246.61       $1,358.2474   $1,358.24   $1,358.20   $1,358.40