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 $208.57   8.216%   $225.7061   $225.71   $225.70   $225.70  
  Purchase #2 $215.62   4.653%   $225.6528   $225.65   $225.65   $225.70  
  Purchase #3 $135.83   12.133%   $152.3103   $152.31   $152.30   $152.30  
  Purchase #4 $199.78   7.727%   $215.217   $215.22   $215.20   $215.20  
  Purchase #5 $55.39   5.144%   $58.2393   $58.24   $58.25   $58.20  
  Purchase #6 $216.48   8.367%   $234.5929   $234.59   $234.60   $234.60  
  Purchase #7 $129.84   3.794%   $134.7661   $134.77   $134.75   $134.80  
  7 purchase totals = $1,161.51       $1,246.4845   $1,246.49   $1,246.45   $1,246.50