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 $196.38   3.212%   $202.6877   $202.69   $202.70   $202.70  
  Purchase #2 $108.27   5.377%   $114.0917   $114.09   $114.10   $114.10  
  Purchase #3 $19.65   6.252%   $20.8785   $20.88   $20.90   $20.90  
  Purchase #4 $80.96   13.410%   $91.8167   $91.82   $91.80   $91.80  
  Purchase #5 $229.79   6.397%   $244.4897   $244.49   $244.50   $244.50  
  Purchase #6 $104.51   12.162%   $117.2205   $117.22   $117.20   $117.20  
  Purchase #7 $204.49   9.397%   $223.7059   $223.71   $223.70   $223.70  
  7 purchase totals = $944.05       $1,014.8907   $1,014.90   $1,014.90   $1,014.90