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 $53.32   11.307%   $59.3489   $59.35   $59.35   $59.30  
  Purchase #2 $174.37   4.799%   $182.738   $182.74   $182.75   $182.70  
  Purchase #3 $234.39   5.494%   $247.2674   $247.27   $247.25   $247.30  
  Purchase #4 $197.34   3.483%   $204.2134   $204.21   $204.20   $204.20  
  Purchase #5 $200.84   11.599%   $224.1354   $224.14   $224.15   $224.10  
  Purchase #6 $190.69   7.278%   $204.5684   $204.57   $204.55   $204.60  
  Purchase #7 $183.66   11.347%   $204.4999   $204.50   $204.50   $204.50  
  7 purchase totals = $1,234.61       $1,326.7714   $1,326.78   $1,326.75   $1,326.70