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 $62.54   10.190%   $68.9128   $68.91   $68.90   $68.90  
  Purchase #2 $175.80   6.689%   $187.5593   $187.56   $187.55   $187.60  
  Purchase #3 $114.38   10.209%   $126.0571   $126.06   $126.05   $126.10  
  Purchase #4 $206.31   5.690%   $218.049   $218.05   $218.05   $218.00  
  Purchase #5 $59.99   13.326%   $67.9843   $67.98   $68.00   $68.00  
  Purchase #6 $211.31   6.220%   $224.4535   $224.45   $224.45   $224.50  
  Purchase #7 $55.46   10.236%   $61.1369   $61.14   $61.15   $61.10  
  7 purchase totals = $885.79       $954.1529   $954.15   $954.15   $954.20