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 $65.47   11.120%   $72.7503   $72.75   $72.75   $72.80  
  Purchase #2 $84.32   3.127%   $86.9567   $86.96   $86.95   $87.00  
  Purchase #3 $218.99   8.410%   $237.4071   $237.41   $237.40   $237.40  
  Purchase #4 $119.30   6.501%   $127.0557   $127.06   $127.05   $127.10  
  Purchase #5 $239.70   6.125%   $254.3816   $254.38   $254.40   $254.40  
  Purchase #6 $197.92   6.692%   $211.1648   $211.16   $211.15   $211.20  
  Purchase #7 $101.54   3.184%   $104.773   $104.77   $104.75   $104.80  
  7 purchase totals = $1,027.24       $1,094.4892   $1,094.49   $1,094.45   $1,094.70