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 $57.33   11.511%   $63.9293   $63.93   $63.95   $63.90  
  Purchase #2 $239.51   7.825%   $258.2517   $258.25   $258.25   $258.30  
  Purchase #3 $194.55   5.553%   $205.3534   $205.35   $205.35   $205.40  
  Purchase #4 $37.81   8.767%   $41.1248   $41.12   $41.10   $41.10  
  Purchase #5 $146.41   9.416%   $160.196   $160.20   $160.20   $160.20  
  Purchase #6 $221.50   11.777%   $247.5861   $247.59   $247.60   $247.60  
  Purchase #7 $120.41   4.376%   $125.6791   $125.68   $125.70   $125.70  
  7 purchase totals = $1,017.52       $1,102.1204   $1,102.12   $1,102.15   $1,102.20