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 $24.63   8.302%   $26.6748   $26.67   $26.65   $26.70  
  Purchase #2 $85.94   11.677%   $95.9752   $95.98   $96.00   $96.00  
  Purchase #3 $245.55   11.195%   $273.0393   $273.04   $273.05   $273.00  
  Purchase #4 $186.98   12.811%   $210.934   $210.93   $210.95   $210.90  
  Purchase #5 $218.74   9.846%   $240.2771   $240.28   $240.30   $240.30  
  Purchase #6 $191.85   8.297%   $207.7678   $207.77   $207.75   $207.80  
  Purchase #7 $93.55   12.577%   $105.3158   $105.32   $105.30   $105.30  
  7 purchase totals = $1,047.24       $1,159.9840   $1,159.99   $1,160.00   $1,160.00