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 $114.56   9.640%   $125.6036   $125.60   $125.60   $125.60  
  Purchase #2 $79.41   3.620%   $82.2846   $82.28   $82.30   $82.30  
  Purchase #3 $231.44   7.689%   $249.2354   $249.24   $249.25   $249.20  
  Purchase #4 $105.26   7.815%   $113.4861   $113.49   $113.50   $113.50  
  Purchase #5 $203.75   3.558%   $210.9994   $211.00   $211.00   $211.00  
  Purchase #6 $111.56   9.743%   $122.4293   $122.43   $122.45   $122.40  
  Purchase #7 $65.82   10.276%   $72.5837   $72.58   $72.60   $72.60  
  7 purchase totals = $911.80       $976.6221   $976.62   $976.70   $976.60