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 $126.75   8.819%   $137.9281   $137.93   $137.95   $137.90  
  Purchase #2 $131.45   10.745%   $145.5743   $145.57   $145.55   $145.60  
  Purchase #3 $228.36   5.396%   $240.6823   $240.68   $240.70   $240.70  
  Purchase #4 $10.35   10.751%   $11.4627   $11.46   $11.45   $11.50  
  Purchase #5 $182.38   13.766%   $207.4864   $207.49   $207.50   $207.50  
  Purchase #6 $205.65   4.251%   $214.3922   $214.39   $214.40   $214.40  
  Purchase #7 $160.60   3.453%   $166.1455   $166.15   $166.15   $166.10  
  7 purchase totals = $1,045.54       $1,123.6715   $1,123.67   $1,123.70   $1,123.70