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 $84.92   12.571%   $95.5953   $95.60   $95.60   $95.60  
  Purchase #2 $222.77   4.692%   $233.2224   $233.22   $233.20   $233.20  
  Purchase #3 $112.26   7.384%   $120.5493   $120.55   $120.55   $120.50  
  Purchase #4 $160.28   8.558%   $173.9968   $174.00   $174.00   $174.00  
  Purchase #5 $190.90   7.443%   $205.1087   $205.11   $205.10   $205.10  
  Purchase #6 $82.35   11.719%   $92.0006   $92.00   $92.00   $92.00  
  Purchase #7 $145.80   5.179%   $153.351   $153.35   $153.35   $153.40  
  7 purchase totals = $999.28       $1,073.8241   $1,073.83   $1,073.80   $1,073.80