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 $62.55   10.603%   $69.1822   $69.18   $69.20   $69.20  
  Purchase #2 $210.71   6.851%   $225.1457   $225.15   $225.15   $225.10  
  Purchase #3 $213.71   5.174%   $224.7674   $224.77   $224.75   $224.80  
  Purchase #4 $139.84   8.738%   $152.0592   $152.06   $152.05   $152.10  
  Purchase #5 $126.36   12.827%   $142.5682   $142.57   $142.55   $142.60  
  Purchase #6 $127.66   4.195%   $133.0153   $133.02   $133.00   $133.00  
  Purchase #7 $114.74   9.853%   $126.0453   $126.05   $126.05   $126.00  
  7 purchase totals = $995.57       $1,072.7833   $1,072.80   $1,072.75   $1,072.80