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 $87.94   7.177%   $94.2515   $94.25   $94.25   $94.30  
  Purchase #2 $24.26   8.700%   $26.3706   $26.37   $26.35   $26.40  
  Purchase #3 $164.96   8.564%   $179.0872   $179.09   $179.10   $179.10  
  Purchase #4 $79.78   13.295%   $90.3868   $90.39   $90.40   $90.40  
  Purchase #5 $232.68   7.200%   $249.433   $249.43   $249.45   $249.40  
  Purchase #6 $205.34   6.595%   $218.8822   $218.88   $218.90   $218.90  
  Purchase #7 $147.96   11.197%   $164.5271   $164.53   $164.55   $164.50  
  7 purchase totals = $942.92       $1,022.9384   $1,022.94   $1,023.00   $1,023.00