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 $78.29   9.874%   $86.0204   $86.02   $86.00   $86.00  
  Purchase #2 $125.36   4.785%   $131.3585   $131.36   $131.35   $131.40  
  Purchase #3 $9.94   13.624%   $11.2942   $11.29   $11.30   $11.30  
  Purchase #4 $197.56   7.168%   $211.7211   $211.72   $211.70   $211.70  
  Purchase #5 $237.74   13.219%   $269.1669   $269.17   $269.15   $269.20  
  Purchase #6 $51.49   3.479%   $53.2813   $53.28   $53.30   $53.30  
  Purchase #7 $198.42   7.449%   $213.2003   $213.20   $213.20   $213.20  
  7 purchase totals = $898.80       $976.0427   $976.04   $976.00   $976.10