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 $187.27   3.826%   $194.435   $194.44   $194.45   $194.40  
  Purchase #2 $129.79   10.141%   $142.952   $142.95   $142.95   $143.00  
  Purchase #3 $250.97   3.203%   $259.0086   $259.01   $259.00   $259.00  
  Purchase #4 $246.59   9.158%   $269.1727   $269.17   $269.15   $269.20  
  Purchase #5 $57.83   4.667%   $60.5289   $60.53   $60.55   $60.50  
  Purchase #6 $59.50   7.484%   $63.953   $63.95   $63.95   $64.00  
  Purchase #7 $67.39   11.419%   $75.0853   $75.09   $75.10   $75.10  
  7 purchase totals = $999.34       $1,065.1355   $1,065.14   $1,065.15   $1,065.20