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 $118.81   4.153%   $123.7442   $123.74   $123.75   $123.70  
  Purchase #2 $185.48   6.589%   $197.7013   $197.70   $197.70   $197.70  
  Purchase #3 $45.87   10.309%   $50.5987   $50.60   $50.60   $50.60  
  Purchase #4 $63.42   5.159%   $66.6918   $66.69   $66.70   $66.70  
  Purchase #5 $137.42   9.355%   $150.2756   $150.28   $150.30   $150.30  
  Purchase #6 $89.25   5.235%   $93.9222   $93.92   $93.90   $93.90  
  Purchase #7 $74.70   4.586%   $78.1257   $78.13   $78.15   $78.10  
  7 purchase totals = $714.95       $761.0595   $761.06   $761.10   $761.00