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 $32.69   6.109%   $34.687   $34.69   $34.70   $34.70  
  Purchase #2 $239.48   12.631%   $269.7287   $269.73   $269.75   $269.70  
  Purchase #3 $76.90   13.564%   $87.3307   $87.33   $87.35   $87.30  
  Purchase #4 $111.45   10.461%   $123.1088   $123.11   $123.10   $123.10  
  Purchase #5 $143.85   6.514%   $153.2204   $153.22   $153.20   $153.20  
  Purchase #6 $186.27   4.849%   $195.3022   $195.30   $195.30   $195.30  
  Purchase #7 $65.58   10.773%   $72.6449   $72.64   $72.65   $72.60  
  7 purchase totals = $856.22       $936.0227   $936.02   $936.05   $935.90