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 $32.48   5.764%   $34.3521   $34.35   $34.35   $34.40  
  Purchase #2 $172.31   3.443%   $178.2426   $178.24   $178.25   $178.20  
  Purchase #3 $119.67   5.868%   $126.6922   $126.69   $126.70   $126.70  
  Purchase #4 $73.91   10.824%   $81.91   $81.91   $81.90   $81.90  
  Purchase #5 $203.57   9.869%   $223.6603   $223.66   $223.65   $223.70  
  Purchase #6 $188.85   4.652%   $197.6353   $197.64   $197.65   $197.60  
  Purchase #7 $211.70   6.474%   $225.4055   $225.41   $225.40   $225.40  
  7 purchase totals = $1,002.49       $1,067.8980   $1,067.90   $1,067.90   $1,067.90