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 $58.35   7.571%   $62.7677   $62.77   $62.75   $62.80  
  Purchase #2 $172.61   13.668%   $196.2023   $196.20   $196.20   $196.20  
  Purchase #3 $31.43   8.151%   $33.9919   $33.99   $34.00   $34.00  
  Purchase #4 $95.46   13.554%   $108.3986   $108.40   $108.40   $108.40  
  Purchase #5 $132.42   10.805%   $146.728   $146.73   $146.75   $146.70  
  Purchase #6 $122.77   4.739%   $128.5881   $128.59   $128.60   $128.60  
  Purchase #7 $61.73   12.274%   $69.3067   $69.31   $69.30   $69.30  
  7 purchase totals = $674.77       $745.9833   $745.99   $746.00   $746.00