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 $211.95   10.751%   $234.7367   $234.74   $234.75   $234.70  
  Purchase #2 $232.97   11.314%   $259.3282   $259.33   $259.35   $259.30  
  Purchase #3 $75.90   5.578%   $80.1337   $80.13   $80.15   $80.10  
  Purchase #4 $179.68   6.149%   $190.7285   $190.73   $190.75   $190.70  
  Purchase #5 $123.28   7.468%   $132.4866   $132.49   $132.50   $132.50  
  Purchase #6 $225.54   11.433%   $251.326   $251.33   $251.35   $251.30  
  Purchase #7 $201.39   8.491%   $218.49   $218.49   $218.50   $218.50  
  7 purchase totals = $1,250.71       $1,367.2297   $1,367.24   $1,367.35   $1,367.10