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 $85.43   8.815%   $92.9607   $92.96   $92.95   $93.00  
  Purchase #2 $213.98   6.594%   $228.0898   $228.09   $228.10   $228.10  
  Purchase #3 $188.40   10.567%   $208.3082   $208.31   $208.30   $208.30  
  Purchase #4 $179.99   11.365%   $200.4459   $200.45   $200.45   $200.40  
  Purchase #5 $98.55   6.783%   $105.2346   $105.23   $105.25   $105.20  
  Purchase #6 $139.29   8.625%   $151.3038   $151.30   $151.30   $151.30  
  Purchase #7 $162.81   5.166%   $171.2208   $171.22   $171.20   $171.20  
  7 purchase totals = $1,068.45       $1,157.5638   $1,157.56   $1,157.55   $1,157.50