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 $84.30   13.261%   $95.479   $95.48   $95.50   $95.50  
  Purchase #2 $9.82   12.112%   $11.0094   $11.01   $11.00   $11.00  
  Purchase #3 $84.42   12.849%   $95.2671   $95.27   $95.25   $95.30  
  Purchase #4 $164.63   5.217%   $173.2187   $173.22   $173.20   $173.20  
  Purchase #5 $177.55   7.806%   $191.4096   $191.41   $191.40   $191.40  
  Purchase #6 $201.94   8.440%   $218.9837   $218.98   $219.00   $219.00  
  Purchase #7 $230.76   4.488%   $241.1165   $241.12   $241.10   $241.10  
  7 purchase totals = $953.42       $1,026.4840   $1,026.49   $1,026.45   $1,026.50