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 $64.61   8.244%   $69.9364   $69.94   $69.95   $69.90  
  Purchase #2 $207.81   8.243%   $224.9398   $224.94   $224.95   $224.90  
  Purchase #3 $22.48   7.195%   $24.0974   $24.10   $24.10   $24.10  
  Purchase #4 $169.85   10.716%   $188.0511   $188.05   $188.05   $188.10  
  Purchase #5 $185.98   13.356%   $210.8195   $210.82   $210.80   $210.80  
  Purchase #6 $161.93   12.678%   $182.4595   $182.46   $182.45   $182.50  
  Purchase #7 $184.67   10.620%   $204.282   $204.28   $204.30   $204.30  
  7 purchase totals = $997.33       $1,104.5857   $1,104.59   $1,104.60   $1,104.60