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 $112.91   5.343%   $118.9428   $118.94   $118.95   $118.90  
  Purchase #2 $41.62   12.575%   $46.8537   $46.85   $46.85   $46.90  
  Purchase #3 $52.64   3.605%   $54.5377   $54.54   $54.55   $54.50  
  Purchase #4 $109.51   4.764%   $114.7271   $114.73   $114.75   $114.70  
  Purchase #5 $184.98   4.664%   $193.6075   $193.61   $193.60   $193.60  
  Purchase #6 $31.69   6.196%   $33.6535   $33.65   $33.65   $33.70  
  Purchase #7 $177.58   11.344%   $197.7247   $197.72   $197.70   $197.70  
  7 purchase totals = $710.93       $760.0470   $760.04   $760.05   $760.00