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 $144.65   8.383%   $156.776   $156.78   $156.80   $156.80  
  Purchase #2 $24.80   5.138%   $26.0742   $26.07   $26.05   $26.10  
  Purchase #3 $71.31   6.700%   $76.0878   $76.09   $76.10   $76.10  
  Purchase #4 $49.75   8.601%   $54.029   $54.03   $54.05   $54.00  
  Purchase #5 $61.85   13.461%   $70.1756   $70.18   $70.20   $70.20  
  Purchase #6 $160.28   6.114%   $170.0795   $170.08   $170.10   $170.10  
  Purchase #7 $163.38   4.591%   $170.8808   $170.88   $170.90   $170.90  
  7 purchase totals = $676.02       $724.1029   $724.11   $724.20   $724.20