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 $90.38   5.728%   $95.557   $95.56   $95.55   $95.60  
  Purchase #2 $177.75   7.690%   $191.419   $191.42   $191.40   $191.40  
  Purchase #3 $147.81   7.448%   $158.8189   $158.82   $158.80   $158.80  
  Purchase #4 $176.63   5.633%   $186.5796   $186.58   $186.60   $186.60  
  Purchase #5 $180.25   7.227%   $193.2767   $193.28   $193.30   $193.30  
  Purchase #6 $162.86   9.803%   $178.8252   $178.83   $178.85   $178.80  
  Purchase #7 $58.98   3.745%   $61.1888   $61.19   $61.20   $61.20  
  7 purchase totals = $994.66       $1,065.6652   $1,065.68   $1,065.70   $1,065.70