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 $197.36   5.368%   $207.9543   $207.95   $207.95   $208.00  
  Purchase #2 $220.95   4.686%   $231.3037   $231.30   $231.30   $231.30  
  Purchase #3 $174.86   13.195%   $197.9328   $197.93   $197.95   $197.90  
  Purchase #4 $160.90   11.367%   $179.1895   $179.19   $179.20   $179.20  
  Purchase #5 $77.47   7.621%   $83.374   $83.37   $83.35   $83.40  
  Purchase #6 $146.49   5.629%   $154.7359   $154.74   $154.75   $154.70  
  Purchase #7 $51.87   3.564%   $53.7186   $53.72   $53.70   $53.70  
  7 purchase totals = $1,029.90       $1,108.2088   $1,108.20   $1,108.20   $1,108.20