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 $90.61   5.360%   $95.4667   $95.47   $95.45   $95.50  
  Purchase #2 $142.89   10.187%   $157.4462   $157.45   $157.45   $157.40  
  Purchase #3 $186.57   10.296%   $205.7792   $205.78   $205.80   $205.80  
  Purchase #4 $63.40   8.245%   $68.6273   $68.63   $68.65   $68.60  
  Purchase #5 $54.55   11.766%   $60.9684   $60.97   $60.95   $61.00  
  Purchase #6 $51.25   6.785%   $54.7273   $54.73   $54.75   $54.70  
  Purchase #7 $222.87   4.412%   $232.703   $232.70   $232.70   $232.70  
  7 purchase totals = $812.14       $875.7181   $875.73   $875.75   $875.70