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 $174.41   12.239%   $195.756   $195.76   $195.75   $195.80  
  Purchase #2 $194.74   4.211%   $202.9405   $202.94   $202.95   $202.90  
  Purchase #3 $80.71   3.334%   $83.4009   $83.40   $83.40   $83.40  
  Purchase #4 $51.96   12.501%   $58.4555   $58.46   $58.45   $58.50  
  Purchase #5 $138.49   4.186%   $144.2872   $144.29   $144.30   $144.30  
  Purchase #6 $139.61   4.688%   $146.1549   $146.15   $146.15   $146.20  
  Purchase #7 $201.78   12.520%   $227.0429   $227.04   $227.05   $227.00  
  7 purchase totals = $981.70       $1,058.0379   $1,058.04   $1,058.05   $1,058.10