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 $58.48   6.264%   $62.1432   $62.14   $62.15   $62.10  
  Purchase #2 $170.59   10.618%   $188.7032   $188.70   $188.70   $188.70  
  Purchase #3 $126.62   11.815%   $141.5802   $141.58   $141.60   $141.60  
  Purchase #4 $122.71   9.602%   $134.4926   $134.49   $134.50   $134.50  
  Purchase #5 $181.81   7.279%   $195.0439   $195.04   $195.05   $195.00  
  Purchase #6 $162.80   9.272%   $177.8948   $177.89   $177.90   $177.90  
  Purchase #7 $216.26   7.366%   $232.1897   $232.19   $232.20   $232.20  
  7 purchase totals = $1,039.27       $1,132.0476   $1,132.03   $1,132.10   $1,132.00