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 $59.40   9.872%   $65.264   $65.26   $65.25   $65.30  
  Purchase #2 $237.57   13.312%   $269.1953   $269.20   $269.20   $269.20  
  Purchase #3 $204.41   3.208%   $210.9675   $210.97   $210.95   $211.00  
  Purchase #4 $226.76   4.401%   $236.7397   $236.74   $236.75   $236.70  
  Purchase #5 $40.46   7.616%   $43.5414   $43.54   $43.55   $43.50  
  Purchase #6 $37.99   5.548%   $40.0977   $40.10   $40.10   $40.10  
  Purchase #7 $198.73   8.817%   $216.252   $216.25   $216.25   $216.30  
  7 purchase totals = $1,005.32       $1,082.0576   $1,082.06   $1,082.05   $1,082.10