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 $87.49   9.667%   $95.9477   $95.95   $95.95   $95.90  
  Purchase #2 $150.69   10.263%   $166.1553   $166.16   $166.15   $166.20  
  Purchase #3 $95.80   6.438%   $101.9676   $101.97   $101.95   $102.00  
  Purchase #4 $73.45   11.410%   $81.8306   $81.83   $81.85   $81.80  
  Purchase #5 $125.48   4.413%   $131.0174   $131.02   $131.00   $131.00  
  Purchase #6 $82.45   5.227%   $86.7597   $86.76   $86.75   $86.80  
  Purchase #7 $164.57   4.527%   $172.0201   $172.02   $172.00   $172.00  
  7 purchase totals = $779.93       $835.6984   $835.71   $835.65   $835.70