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 $86.26   8.624%   $93.6991   $93.70   $93.70   $93.70  
  Purchase #2 $248.57   3.395%   $257.009   $257.01   $257.00   $257.00  
  Purchase #3 $119.53   6.707%   $127.5469   $127.55   $127.55   $127.50  
  Purchase #4 $211.28   13.124%   $239.0084   $239.01   $239.00   $239.00  
  Purchase #5 $220.33   12.866%   $248.6777   $248.68   $248.70   $248.70  
  Purchase #6 $211.92   12.168%   $237.7064   $237.71   $237.70   $237.70  
  Purchase #7 $39.31   4.595%   $41.1163   $41.12   $41.10   $41.10  
  7 purchase totals = $1,137.20       $1,244.7638   $1,244.78   $1,244.75   $1,244.70