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 $67.49   3.283%   $69.7057   $69.71   $69.70   $69.70  
  Purchase #2 $153.71   13.835%   $174.9758   $174.98   $175.00   $175.00  
  Purchase #3 $149.78   4.809%   $156.9829   $156.98   $157.00   $157.00  
  Purchase #4 $58.99   11.500%   $65.7739   $65.77   $65.75   $65.80  
  Purchase #5 $250.60   5.213%   $263.6638   $263.66   $263.65   $263.70  
  Purchase #6 $57.33   12.735%   $64.631   $64.63   $64.65   $64.60  
  Purchase #7 $234.97   7.690%   $253.0392   $253.04   $253.05   $253.00  
  7 purchase totals = $972.87       $1,048.7723   $1,048.77   $1,048.80   $1,048.80