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 $161.95   8.116%   $175.0939   $175.09   $175.10   $175.10  
  Purchase #2 $212.87   12.368%   $239.1978   $239.20   $239.20   $239.20  
  Purchase #3 $170.60   12.136%   $191.304   $191.30   $191.30   $191.30  
  Purchase #4 $146.45   11.608%   $163.4499   $163.45   $163.45   $163.40  
  Purchase #5 $55.96   4.141%   $58.2773   $58.28   $58.30   $58.30  
  Purchase #6 $165.64   9.547%   $181.4537   $181.45   $181.45   $181.50  
  Purchase #7 $62.95   7.105%   $67.4226   $67.42   $67.40   $67.40  
  7 purchase totals = $976.42       $1,076.1992   $1,076.19   $1,076.20   $1,076.20