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 $32.69   12.871%   $36.8975   $36.90   $36.90   $36.90  
  Purchase #2 $69.98   8.549%   $75.9626   $75.96   $75.95   $76.00  
  Purchase #3 $116.36   8.451%   $126.1936   $126.19   $126.20   $126.20  
  Purchase #4 $46.75   13.785%   $53.1945   $53.19   $53.20   $53.20  
  Purchase #5 $116.36   4.870%   $122.0267   $122.03   $122.05   $122.00  
  Purchase #6 $173.49   6.835%   $185.348   $185.35   $185.35   $185.30  
  Purchase #7 $150.43   3.436%   $155.5988   $155.60   $155.60   $155.60  
  7 purchase totals = $706.06       $755.2217   $755.22   $755.25   $755.20