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 $68.39   12.760%   $77.1166   $77.12   $77.10   $77.10  
  Purchase #2 $190.48   9.474%   $208.5261   $208.53   $208.55   $208.50  
  Purchase #3 $169.81   5.468%   $179.0952   $179.10   $179.10   $179.10  
  Purchase #4 $134.77   10.676%   $149.158   $149.16   $149.15   $149.20  
  Purchase #5 $183.63   9.607%   $201.2713   $201.27   $201.25   $201.30  
  Purchase #6 $72.25   5.554%   $76.2628   $76.26   $76.25   $76.30  
  Purchase #7 $191.34   6.602%   $203.9723   $203.97   $203.95   $204.00  
  7 purchase totals = $1,010.67       $1,095.4023   $1,095.41   $1,095.35   $1,095.50