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 $60.35   11.429%   $67.2474   $67.25   $67.25   $67.20  
  Purchase #2 $179.83   5.435%   $189.6038   $189.60   $189.60   $189.60  
  Purchase #3 $64.53   4.154%   $67.2106   $67.21   $67.20   $67.20  
  Purchase #4 $127.99   13.819%   $145.6769   $145.68   $145.70   $145.70  
  Purchase #5 $26.73   13.124%   $30.238   $30.24   $30.25   $30.20  
  Purchase #6 $69.46   6.486%   $73.9652   $73.97   $73.95   $74.00  
  Purchase #7 $150.49   5.544%   $158.8332   $158.83   $158.85   $158.80  
  7 purchase totals = $679.38       $732.7751   $732.78   $732.80   $732.70