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 $194.29   3.257%   $200.618   $200.62   $200.60   $200.60  
  Purchase #2 $224.51   10.623%   $248.3597   $248.36   $248.35   $248.40  
  Purchase #3 $119.49   10.226%   $131.709   $131.71   $131.70   $131.70  
  Purchase #4 $169.82   7.639%   $182.7925   $182.79   $182.80   $182.80  
  Purchase #5 $213.68   5.259%   $224.9174   $224.92   $224.90   $224.90  
  Purchase #6 $193.50   13.231%   $219.102   $219.10   $219.10   $219.10  
  Purchase #7 $52.41   13.839%   $59.663   $59.66   $59.65   $59.70  
  7 purchase totals = $1,167.70       $1,267.1616   $1,267.16   $1,267.10   $1,267.20