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 $117.25   8.262%   $126.9372   $126.94   $126.95   $126.90  
  Purchase #2 $32.82   10.436%   $36.2451   $36.25   $36.25   $36.20  
  Purchase #3 $232.78   12.617%   $262.1499   $262.15   $262.15   $262.10  
  Purchase #4 $162.43   6.619%   $173.1812   $173.18   $173.20   $173.20  
  Purchase #5 $219.79   4.506%   $229.6937   $229.69   $229.70   $229.70  
  Purchase #6 $153.57   11.645%   $171.4532   $171.45   $171.45   $171.50  
  Purchase #7 $206.79   6.176%   $219.5614   $219.56   $219.55   $219.60  
  7 purchase totals = $1,125.43       $1,219.2217   $1,219.22   $1,219.25   $1,219.20