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 $207.81   12.382%   $233.541   $233.54   $233.55   $233.50  
  Purchase #2 $28.27   3.126%   $29.1537   $29.15   $29.15   $29.20  
  Purchase #3 $161.96   11.603%   $180.7522   $180.75   $180.75   $180.80  
  Purchase #4 $87.88   3.472%   $90.9312   $90.93   $90.95   $90.90  
  Purchase #5 $66.51   3.395%   $68.768   $68.77   $68.75   $68.80  
  Purchase #6 $235.55   4.174%   $245.3819   $245.38   $245.40   $245.40  
  Purchase #7 $196.55   4.617%   $205.6247   $205.62   $205.60   $205.60  
  7 purchase totals = $984.53       $1,054.1527   $1,054.14   $1,054.15   $1,054.20