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 $67.64   13.771%   $76.9547   $76.95   $76.95   $77.00  
  Purchase #2 $98.77   3.741%   $102.465   $102.47   $102.45   $102.50  
  Purchase #3 $16.41   13.489%   $18.6235   $18.62   $18.60   $18.60  
  Purchase #4 $162.83   6.583%   $173.5491   $173.55   $173.55   $173.50  
  Purchase #5 $127.84   6.485%   $136.1304   $136.13   $136.15   $136.10  
  Purchase #6 $162.58   6.761%   $173.572   $173.57   $173.55   $173.60  
  Purchase #7 $233.51   9.848%   $256.5061   $256.51   $256.50   $256.50  
  7 purchase totals = $869.58       $937.8008   $937.80   $937.75   $937.80