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 $59.84   3.493%   $61.9302   $61.93   $61.95   $61.90  
  Purchase #2 $184.42   5.153%   $193.9232   $193.92   $193.90   $193.90  
  Purchase #3 $34.70   7.377%   $37.2598   $37.26   $37.25   $37.30  
  Purchase #4 $155.34   7.182%   $166.4965   $166.50   $166.50   $166.50  
  Purchase #5 $177.55   7.341%   $190.5839   $190.58   $190.60   $190.60  
  Purchase #6 $146.81   11.539%   $163.7504   $163.75   $163.75   $163.80  
  Purchase #7 $10.62   4.322%   $11.079   $11.08   $11.10   $11.10  
  7 purchase totals = $769.28       $825.0230   $825.02   $825.05   $825.10