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 $241.64   5.402%   $254.6934   $254.69   $254.70   $254.70  
  Purchase #2 $10.99   3.205%   $11.3422   $11.34   $11.35   $11.30  
  Purchase #3 $164.90   7.571%   $177.3846   $177.38   $177.40   $177.40  
  Purchase #4 $170.92   12.611%   $192.4747   $192.47   $192.45   $192.50  
  Purchase #5 $10.73   9.362%   $11.7345   $11.73   $11.75   $11.70  
  Purchase #6 $229.56   12.511%   $258.2803   $258.28   $258.30   $258.30  
  Purchase #7 $194.89   7.203%   $208.9279   $208.93   $208.95   $208.90  
  7 purchase totals = $1,023.63       $1,114.8376   $1,114.82   $1,114.90   $1,114.80