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 $247.44   8.136%   $267.5717   $267.57   $267.55   $267.60  
  Purchase #2 $220.37   7.435%   $236.7545   $236.75   $236.75   $236.80  
  Purchase #3 $15.48   5.440%   $16.3221   $16.32   $16.30   $16.30  
  Purchase #4 $130.94   3.809%   $135.9275   $135.93   $135.95   $135.90  
  Purchase #5 $131.56   12.737%   $148.3168   $148.32   $148.30   $148.30  
  Purchase #6 $231.87   11.796%   $259.2214   $259.22   $259.20   $259.20  
  Purchase #7 $91.73   3.765%   $95.1836   $95.18   $95.20   $95.20  
  7 purchase totals = $1,069.39       $1,159.2976   $1,159.29   $1,159.25   $1,159.30