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 $218.54   7.843%   $235.6801   $235.68   $235.70   $235.70  
  Purchase #2 $58.41   4.611%   $61.1033   $61.10   $61.10   $61.10  
  Purchase #3 $214.86   13.448%   $243.7544   $243.75   $243.75   $243.80  
  Purchase #4 $10.27   5.727%   $10.8582   $10.86   $10.85   $10.90  
  Purchase #5 $19.94   13.487%   $22.6293   $22.63   $22.65   $22.60  
  Purchase #6 $182.40   10.642%   $201.811   $201.81   $201.80   $201.80  
  Purchase #7 $247.73   11.413%   $276.0034   $276.00   $276.00   $276.00  
  7 purchase totals = $952.15       $1,051.8397   $1,051.83   $1,051.85   $1,051.90