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 $208.45   13.727%   $237.0639   $237.06   $237.05   $237.10  
  Purchase #2 $198.90   7.423%   $213.6643   $213.66   $213.65   $213.70  
  Purchase #3 $180.84   13.348%   $204.9785   $204.98   $205.00   $205.00  
  Purchase #4 $124.55   8.166%   $134.7208   $134.72   $134.70   $134.70  
  Purchase #5 $135.33   8.775%   $147.2052   $147.21   $147.20   $147.20  
  Purchase #6 $170.27   9.170%   $185.8838   $185.88   $185.90   $185.90  
  Purchase #7 $157.88   3.109%   $162.7885   $162.79   $162.80   $162.80  
  7 purchase totals = $1,176.22       $1,286.3050   $1,286.30   $1,286.30   $1,286.40