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 $85.81   10.790%   $95.0689   $95.07   $95.05   $95.10  
  Purchase #2 $50.57   7.336%   $54.2798   $54.28   $54.30   $54.30  
  Purchase #3 $226.80   8.625%   $246.3615   $246.36   $246.35   $246.40  
  Purchase #4 $249.47   3.658%   $258.5956   $258.60   $258.60   $258.60  
  Purchase #5 $213.89   11.589%   $238.6777   $238.68   $238.70   $238.70  
  Purchase #6 $124.54   10.291%   $137.3564   $137.36   $137.35   $137.40  
  Purchase #7 $242.54   9.733%   $266.1464   $266.15   $266.15   $266.10  
  7 purchase totals = $1,193.62       $1,296.4863   $1,296.50   $1,296.50   $1,296.60