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 $104.70   8.832%   $113.9471   $113.95   $113.95   $113.90  
  Purchase #2 $33.67   4.257%   $35.1033   $35.10   $35.10   $35.10  
  Purchase #3 $163.45   9.701%   $179.3063   $179.31   $179.30   $179.30  
  Purchase #4 $67.31   6.492%   $71.6798   $71.68   $71.70   $71.70  
  Purchase #5 $186.68   13.221%   $211.361   $211.36   $211.35   $211.40  
  Purchase #6 $105.42   9.159%   $115.0754   $115.08   $115.10   $115.10  
  Purchase #7 $169.62   5.851%   $179.5445   $179.54   $179.55   $179.50  
  7 purchase totals = $830.85       $906.0174   $906.02   $906.05   $906.00