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 $79.86   7.622%   $85.9469   $85.95   $85.95   $85.90  
  Purchase #2 $231.26   5.388%   $243.7203   $243.72   $243.70   $243.70  
  Purchase #3 $36.91   10.394%   $40.7464   $40.75   $40.75   $40.70  
  Purchase #4 $173.75   11.300%   $193.3838   $193.38   $193.40   $193.40  
  Purchase #5 $135.62   4.287%   $141.434   $141.43   $141.45   $141.40  
  Purchase #6 $207.53   4.250%   $216.35   $216.35   $216.35   $216.40  
  Purchase #7 $184.63   4.623%   $193.1654   $193.17   $193.15   $193.20  
  7 purchase totals = $1,049.56       $1,114.7468   $1,114.75   $1,114.75   $1,114.70