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 $178.62   9.813%   $196.148   $196.15   $196.15   $196.10  
  Purchase #2 $49.93   8.872%   $54.3598   $54.36   $54.35   $54.40  
  Purchase #3 $92.39   5.319%   $97.3042   $97.30   $97.30   $97.30  
  Purchase #4 $232.28   13.524%   $263.6935   $263.69   $263.70   $263.70  
  Purchase #5 $200.51   13.700%   $227.9799   $227.98   $228.00   $228.00  
  Purchase #6 $78.73   3.453%   $81.4485   $81.45   $81.45   $81.40  
  Purchase #7 $39.71   13.843%   $45.2071   $45.21   $45.20   $45.20  
  7 purchase totals = $872.17       $966.1410   $966.14   $966.15   $966.10