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 $38.69   13.795%   $44.0273   $44.03   $44.05   $44.00  
  Purchase #2 $151.51   6.421%   $161.2385   $161.24   $161.25   $161.20  
  Purchase #3 $169.99   5.622%   $179.5468   $179.55   $179.55   $179.50  
  Purchase #4 $27.90   6.766%   $29.7877   $29.79   $29.80   $29.80  
  Purchase #5 $170.75   4.542%   $178.5055   $178.51   $178.50   $178.50  
  Purchase #6 $231.65   6.552%   $246.8277   $246.83   $246.85   $246.80  
  Purchase #7 $162.27   7.687%   $174.7437   $174.74   $174.75   $174.70  
  7 purchase totals = $952.76       $1,014.6772   $1,014.69   $1,014.75   $1,014.50