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 $114.49   3.581%   $118.5899   $118.59   $118.60   $118.60  
  Purchase #2 $200.47   5.398%   $211.2914   $211.29   $211.30   $211.30  
  Purchase #3 $84.29   11.746%   $94.1907   $94.19   $94.20   $94.20  
  Purchase #4 $245.32   11.439%   $273.3822   $273.38   $273.40   $273.40  
  Purchase #5 $12.70   13.126%   $14.367   $14.37   $14.35   $14.40  
  Purchase #6 $169.37   6.588%   $180.5281   $180.53   $180.55   $180.50  
  Purchase #7 $181.66   5.287%   $191.2644   $191.26   $191.25   $191.30  
  7 purchase totals = $1,008.30       $1,083.6137   $1,083.61   $1,083.65   $1,083.70