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 $41.80   4.271%   $43.5853   $43.59   $43.60   $43.60  
  Purchase #2 $63.35   11.286%   $70.4997   $70.50   $70.50   $70.50  
  Purchase #3 $173.96   6.361%   $185.0256   $185.03   $185.05   $185.00  
  Purchase #4 $224.78   12.284%   $252.392   $252.39   $252.40   $252.40  
  Purchase #5 $218.25   9.874%   $239.8   $239.80   $239.80   $239.80  
  Purchase #6 $195.45   7.260%   $209.6397   $209.64   $209.65   $209.60  
  Purchase #7 $55.61   9.153%   $60.7   $60.70   $60.70   $60.70  
  7 purchase totals = $973.20       $1,061.6423   $1,061.65   $1,061.70   $1,061.60