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 $193.96   6.593%   $206.7478   $206.75   $206.75   $206.70  
  Purchase #2 $117.80   9.595%   $129.1029   $129.10   $129.10   $129.10  
  Purchase #3 $207.72   9.159%   $226.7451   $226.75   $226.75   $226.70  
  Purchase #4 $119.92   9.668%   $131.5139   $131.51   $131.50   $131.50  
  Purchase #5 $23.26   5.477%   $24.534   $24.53   $24.55   $24.50  
  Purchase #6 $133.28   8.164%   $144.161   $144.16   $144.15   $144.20  
  Purchase #7 $162.88   6.359%   $173.2375   $173.24   $173.25   $173.20  
  7 purchase totals = $958.82       $1,036.0422   $1,036.04   $1,036.05   $1,035.90