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 $182.60   6.213%   $193.9449   $193.94   $193.95   $193.90  
  Purchase #2 $32.43   4.157%   $33.7781   $33.78   $33.80   $33.80  
  Purchase #3 $201.36   6.280%   $214.0054   $214.01   $214.00   $214.00  
  Purchase #4 $175.81   8.487%   $190.731   $190.73   $190.75   $190.70  
  Purchase #5 $247.45   4.677%   $259.0232   $259.02   $259.00   $259.00  
  Purchase #6 $189.72   4.172%   $197.6351   $197.64   $197.65   $197.60  
  Purchase #7 $192.80   9.529%   $211.1719   $211.17   $211.15   $211.20  
  7 purchase totals = $1,222.17       $1,300.2896   $1,300.29   $1,300.30   $1,300.20