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 $22.50   7.526%   $24.1934   $24.19   $24.20   $24.20  
  Purchase #2 $174.33   9.353%   $190.6351   $190.64   $190.65   $190.60  
  Purchase #3 $60.89   13.693%   $69.2277   $69.23   $69.25   $69.20  
  Purchase #4 $70.85   13.864%   $80.6726   $80.67   $80.65   $80.70  
  Purchase #5 $226.34   6.851%   $241.8466   $241.85   $241.85   $241.80  
  Purchase #6 $64.61   6.833%   $69.0248   $69.02   $69.00   $69.00  
  Purchase #7 $51.66   7.305%   $55.4338   $55.43   $55.45   $55.40  
  7 purchase totals = $671.18       $731.0340   $731.03   $731.05   $730.90