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 $196.57   5.329%   $207.0452   $207.05   $207.05   $207.00  
  Purchase #2 $135.38   6.488%   $144.1635   $144.16   $144.15   $144.20  
  Purchase #3 $249.62   5.826%   $264.1629   $264.16   $264.15   $264.20  
  Purchase #4 $60.64   5.653%   $64.068   $64.07   $64.05   $64.10  
  Purchase #5 $239.49   13.796%   $272.53   $272.53   $272.55   $272.50  
  Purchase #6 $87.93   5.506%   $92.7714   $92.77   $92.75   $92.80  
  Purchase #7 $171.79   5.309%   $180.9103   $180.91   $180.90   $180.90  
  7 purchase totals = $1,141.42       $1,225.6513   $1,225.65   $1,225.60   $1,225.70