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 $76.43   12.535%   $86.0105   $86.01   $86.00   $86.00  
  Purchase #2 $229.52   13.736%   $261.0469   $261.05   $261.05   $261.00  
  Purchase #3 $50.47   5.157%   $53.0727   $53.07   $53.05   $53.10  
  Purchase #4 $120.67   7.267%   $129.4391   $129.44   $129.45   $129.40  
  Purchase #5 $197.97   8.438%   $214.6747   $214.67   $214.65   $214.70  
  Purchase #6 $190.98   6.219%   $202.857   $202.86   $202.85   $202.90  
  Purchase #7 $178.29   4.660%   $186.5983   $186.60   $186.60   $186.60  
  7 purchase totals = $1,044.33       $1,133.6992   $1,133.70   $1,133.65   $1,133.70