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 $204.66   3.462%   $211.7453   $211.75   $211.75   $211.70  
  Purchase #2 $92.57   13.822%   $105.365   $105.37   $105.35   $105.40  
  Purchase #3 $179.64   4.658%   $188.0076   $188.01   $188.00   $188.00  
  Purchase #4 $24.97   6.549%   $26.6053   $26.61   $26.60   $26.60  
  Purchase #5 $109.94   3.152%   $113.4053   $113.41   $113.40   $113.40  
  Purchase #6 $179.66   10.282%   $198.1326   $198.13   $198.15   $198.10  
  Purchase #7 $250.36   3.517%   $259.1652   $259.17   $259.15   $259.20  
  7 purchase totals = $1,041.80       $1,102.4263   $1,102.45   $1,102.40   $1,102.40