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 $10.78   4.509%   $11.2661   $11.27   $11.25   $11.30  
  Purchase #2 $218.98   6.693%   $233.6363   $233.64   $233.65   $233.60  
  Purchase #3 $145.78   7.738%   $157.0605   $157.06   $157.05   $157.10  
  Purchase #4 $179.49   12.189%   $201.368   $201.37   $201.35   $201.40  
  Purchase #5 $206.68   7.238%   $221.6395   $221.64   $221.65   $221.60  
  Purchase #6 $23.68   5.287%   $24.932   $24.93   $24.95   $24.90  
  Purchase #7 $162.28   12.624%   $182.7662   $182.77   $182.75   $182.80  
  7 purchase totals = $947.67       $1,032.6686   $1,032.68   $1,032.65   $1,032.70