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 $48.26   9.501%   $52.8452   $52.85   $52.85   $52.80  
  Purchase #2 $94.41   9.614%   $103.4866   $103.49   $103.50   $103.50  
  Purchase #3 $153.66   4.611%   $160.7453   $160.75   $160.75   $160.70  
  Purchase #4 $247.39   3.678%   $256.489   $256.49   $256.50   $256.50  
  Purchase #5 $230.70   9.535%   $252.6972   $252.70   $252.70   $252.70  
  Purchase #6 $133.53   13.262%   $151.2387   $151.24   $151.25   $151.20  
  Purchase #7 $55.87   4.859%   $58.5847   $58.58   $58.60   $58.60  
  7 purchase totals = $963.82       $1,036.0867   $1,036.10   $1,036.15   $1,036.00