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 $202.69   4.424%   $211.657   $211.66   $211.65   $211.70  
  Purchase #2 $238.31   4.239%   $248.412   $248.41   $248.40   $248.40  
  Purchase #3 $38.38   13.326%   $43.4945   $43.49   $43.50   $43.50  
  Purchase #4 $160.26   4.709%   $167.8066   $167.81   $167.80   $167.80  
  Purchase #5 $124.63   4.444%   $130.1686   $130.17   $130.15   $130.20  
  Purchase #6 $130.62   13.564%   $148.3373   $148.34   $148.35   $148.30  
  Purchase #7 $127.51   7.671%   $137.2913   $137.29   $137.30   $137.30  
  7 purchase totals = $1,022.40       $1,087.1673   $1,087.17   $1,087.15   $1,087.20