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 $176.83   13.686%   $201.031   $201.03   $201.05   $201.00  
  Purchase #2 $111.34   3.701%   $115.4607   $115.46   $115.45   $115.50  
  Purchase #3 $155.49   6.404%   $165.4476   $165.45   $165.45   $165.40  
  Purchase #4 $51.97   9.333%   $56.8204   $56.82   $56.80   $56.80  
  Purchase #5 $234.86   12.517%   $264.2574   $264.26   $264.25   $264.30  
  Purchase #6 $186.92   4.358%   $195.066   $195.07   $195.05   $195.10  
  Purchase #7 $60.80   9.778%   $66.745   $66.75   $66.75   $66.70  
  7 purchase totals = $978.21       $1,064.8281   $1,064.84   $1,064.80   $1,064.80