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 $65.47   9.715%   $71.8304   $71.83   $71.85   $71.80  
  Purchase #2 $241.70   11.396%   $269.2441   $269.24   $269.25   $269.20  
  Purchase #3 $14.68   13.591%   $16.6752   $16.68   $16.70   $16.70  
  Purchase #4 $79.50   4.287%   $82.9082   $82.91   $82.90   $82.90  
  Purchase #5 $216.83   4.476%   $226.5353   $226.54   $226.55   $226.50  
  Purchase #6 $112.80   6.817%   $120.4896   $120.49   $120.50   $120.50  
  Purchase #7 $233.54   4.675%   $244.458   $244.46   $244.45   $244.50  
  7 purchase totals = $964.52       $1,032.1408   $1,032.15   $1,032.20   $1,032.10