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 $206.87   12.808%   $233.3659   $233.37   $233.35   $233.40  
  Purchase #2 $108.82   5.354%   $114.6462   $114.65   $114.65   $114.60  
  Purchase #3 $208.89   4.819%   $218.9564   $218.96   $218.95   $219.00  
  Purchase #4 $206.47   5.732%   $218.3049   $218.30   $218.30   $218.30  
  Purchase #5 $206.36   7.815%   $222.487   $222.49   $222.50   $222.50  
  Purchase #6 $36.79   13.526%   $41.7662   $41.77   $41.75   $41.80  
  Purchase #7 $159.56   3.452%   $165.068   $165.07   $165.05   $165.10  
  7 purchase totals = $1,133.76       $1,214.5946   $1,214.61   $1,214.55   $1,214.70