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 $88.59   6.262%   $94.1375   $94.14   $94.15   $94.10  
  Purchase #2 $248.37   13.745%   $282.5085   $282.51   $282.50   $282.50  
  Purchase #3 $187.35   8.638%   $203.5333   $203.53   $203.55   $203.50  
  Purchase #4 $72.50   6.255%   $77.0349   $77.03   $77.05   $77.00  
  Purchase #5 $95.85   5.759%   $101.37   $101.37   $101.35   $101.40  
  Purchase #6 $93.80   12.334%   $105.3693   $105.37   $105.35   $105.40  
  Purchase #7 $84.76   7.508%   $91.1238   $91.12   $91.10   $91.10  
  7 purchase totals = $871.22       $955.0773   $955.07   $955.05   $955.00