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 $212.63   7.226%   $227.9946   $227.99   $228.00   $228.00  
  Purchase #2 $94.76   13.272%   $107.3365   $107.34   $107.35   $107.30  
  Purchase #3 $75.47   8.647%   $81.9959   $82.00   $82.00   $82.00  
  Purchase #4 $155.32   8.565%   $168.6232   $168.62   $168.60   $168.60  
  Purchase #5 $223.62   8.833%   $243.3724   $243.37   $243.35   $243.40  
  Purchase #6 $86.92   13.173%   $98.37   $98.37   $98.35   $98.40  
  Purchase #7 $82.32   5.345%   $86.72   $86.72   $86.70   $86.70  
  7 purchase totals = $931.04       $1,014.4126   $1,014.41   $1,014.35   $1,014.40