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 $123.92   7.479%   $133.188   $133.19   $133.20   $133.20  
  Purchase #2 $124.76   7.714%   $134.384   $134.38   $134.40   $134.40  
  Purchase #3 $250.41   6.633%   $267.0197   $267.02   $267.00   $267.00  
  Purchase #4 $117.51   5.493%   $123.9648   $123.96   $123.95   $124.00  
  Purchase #5 $190.63   5.544%   $201.1985   $201.20   $201.20   $201.20  
  Purchase #6 $230.94   9.673%   $253.2788   $253.28   $253.30   $253.30  
  Purchase #7 $79.29   6.351%   $84.3257   $84.33   $84.35   $84.30  
  7 purchase totals = $1,117.46       $1,197.3595   $1,197.36   $1,197.40   $1,197.40