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 $174.45   11.681%   $194.8275   $194.83   $194.85   $194.80  
  Purchase #2 $52.37   10.821%   $58.037   $58.04   $58.05   $58.00  
  Purchase #3 $82.25   6.161%   $87.3174   $87.32   $87.30   $87.30  
  Purchase #4 $242.63   10.292%   $267.6015   $267.60   $267.60   $267.60  
  Purchase #5 $217.25   5.133%   $228.4014   $228.40   $228.40   $228.40  
  Purchase #6 $216.85   13.581%   $246.3004   $246.30   $246.30   $246.30  
  Purchase #7 $215.56   13.701%   $245.0939   $245.09   $245.10   $245.10  
  7 purchase totals = $1,201.36       $1,327.5791   $1,327.58   $1,327.60   $1,327.50