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 $176.62   10.680%   $195.483   $195.48   $195.50   $195.50  
  Purchase #2 $79.70   11.461%   $88.8344   $88.83   $88.85   $88.80  
  Purchase #3 $9.95   11.731%   $11.1172   $11.12   $11.10   $11.10  
  Purchase #4 $179.79   5.833%   $190.2772   $190.28   $190.30   $190.30  
  Purchase #5 $168.62   12.588%   $189.8459   $189.85   $189.85   $189.80  
  Purchase #6 $181.78   10.535%   $200.9305   $200.93   $200.95   $200.90  
  Purchase #7 $63.87   5.553%   $67.4167   $67.42   $67.40   $67.40  
  7 purchase totals = $860.33       $943.9049   $943.91   $943.95   $943.80