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 $216.94   5.593%   $229.0735   $229.07   $229.05   $229.10  
  Purchase #2 $228.40   13.510%   $259.2568   $259.26   $259.25   $259.30  
  Purchase #3 $76.41   6.266%   $81.1979   $81.20   $81.20   $81.20  
  Purchase #4 $216.27   3.731%   $224.339   $224.34   $224.35   $224.30  
  Purchase #5 $211.98   6.689%   $226.1593   $226.16   $226.15   $226.20  
  Purchase #6 $198.32   3.737%   $205.7312   $205.73   $205.75   $205.70  
  Purchase #7 $44.71   8.394%   $48.463   $48.46   $48.45   $48.50  
  7 purchase totals = $1,193.03       $1,274.2207   $1,274.22   $1,274.20   $1,274.30