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 $85.98   9.817%   $94.4207   $94.42   $94.40   $94.40  
  Purchase #2 $214.90   9.777%   $235.9108   $235.91   $235.90   $235.90  
  Purchase #3 $26.45   11.133%   $29.3947   $29.39   $29.40   $29.40  
  Purchase #4 $247.35   4.859%   $259.3687   $259.37   $259.35   $259.40  
  Purchase #5 $175.71   11.845%   $196.5228   $196.52   $196.50   $196.50  
  Purchase #6 $23.37   13.271%   $26.4714   $26.47   $26.45   $26.50  
  Purchase #7 $175.48   8.671%   $190.6959   $190.70   $190.70   $190.70  
  7 purchase totals = $949.24       $1,032.7850   $1,032.78   $1,032.70   $1,032.80