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 $56.34   10.402%   $62.2005   $62.20   $62.20   $62.20  
  Purchase #2 $242.69   10.774%   $268.8374   $268.84   $268.85   $268.80  
  Purchase #3 $101.54   12.450%   $114.1817   $114.18   $114.20   $114.20  
  Purchase #4 $81.84   12.194%   $91.8196   $91.82   $91.80   $91.80  
  Purchase #5 $236.94   8.839%   $257.8831   $257.88   $257.90   $257.90  
  Purchase #6 $185.94   10.861%   $206.1349   $206.13   $206.15   $206.10  
  Purchase #7 $32.90   3.403%   $34.0196   $34.02   $34.00   $34.00  
  7 purchase totals = $938.19       $1,035.0768   $1,035.07   $1,035.10   $1,035.00