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 $196.26   5.356%   $206.7717   $206.77   $206.75   $206.80  
  Purchase #2 $200.94   13.815%   $228.6999   $228.70   $228.70   $228.70  
  Purchase #3 $24.41   6.514%   $26.0001   $26.00   $26.00   $26.00  
  Purchase #4 $147.61   10.582%   $163.2301   $163.23   $163.25   $163.20  
  Purchase #5 $16.42   13.526%   $18.641   $18.64   $18.65   $18.60  
  Purchase #6 $130.57   12.135%   $146.4147   $146.41   $146.40   $146.40  
  Purchase #7 $168.98   10.658%   $186.9899   $186.99   $187.00   $187.00  
  7 purchase totals = $885.19       $976.7474   $976.74   $976.75   $976.70