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 $211.28   10.155%   $232.7355   $232.74   $232.75   $232.70  
  Purchase #2 $61.58   3.631%   $63.816   $63.82   $63.80   $63.80  
  Purchase #3 $28.25   6.673%   $30.1351   $30.14   $30.15   $30.10  
  Purchase #4 $61.75   11.373%   $68.7728   $68.77   $68.75   $68.80  
  Purchase #5 $243.76   8.668%   $264.8891   $264.89   $264.90   $264.90  
  Purchase #6 $218.35   6.464%   $232.4641   $232.46   $232.45   $232.50  
  Purchase #7 $200.97   8.428%   $217.9078   $217.91   $217.90   $217.90  
  7 purchase totals = $1,025.94       $1,110.7204   $1,110.73   $1,110.70   $1,110.70