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 $222.62   10.868%   $246.8143   $246.81   $246.80   $246.80  
  Purchase #2 $244.92   7.569%   $263.458   $263.46   $263.45   $263.50  
  Purchase #3 $161.94   3.366%   $167.3909   $167.39   $167.40   $167.40  
  Purchase #4 $198.44   4.692%   $207.7508   $207.75   $207.75   $207.80  
  Purchase #5 $48.77   10.613%   $53.946   $53.95   $53.95   $53.90  
  Purchase #6 $236.96   9.208%   $258.7793   $258.78   $258.80   $258.80  
  Purchase #7 $195.27   3.357%   $201.8252   $201.83   $201.85   $201.80  
  7 purchase totals = $1,308.92       $1,399.9645   $1,399.97   $1,400.00   $1,400.00