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 $86.32   8.866%   $93.9731   $93.97   $93.95   $94.00  
  Purchase #2 $188.82   8.108%   $204.1295   $204.13   $204.15   $204.10  
  Purchase #3 $123.99   3.646%   $128.5107   $128.51   $128.50   $128.50  
  Purchase #4 $230.81   9.730%   $253.2678   $253.27   $253.25   $253.30  
  Purchase #5 $241.71   6.592%   $257.6435   $257.64   $257.65   $257.60  
  Purchase #6 $225.69   6.750%   $240.9241   $240.92   $240.90   $240.90  
  Purchase #7 $170.45   7.795%   $183.7366   $183.74   $183.75   $183.70  
  7 purchase totals = $1,267.79       $1,362.1853   $1,362.18   $1,362.15   $1,362.10