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 $54.86   11.352%   $61.0877   $61.09   $61.10   $61.10  
  Purchase #2 $219.78   7.407%   $236.0591   $236.06   $236.05   $236.10  
  Purchase #3 $7.71   5.843%   $8.1605   $8.16   $8.15   $8.20  
  Purchase #4 $17.28   7.530%   $18.5812   $18.58   $18.60   $18.60  
  Purchase #5 $95.90   8.116%   $103.6832   $103.68   $103.70   $103.70  
  Purchase #6 $58.63   12.563%   $65.9957   $66.00   $66.00   $66.00  
  Purchase #7 $248.57   7.293%   $266.6982   $266.70   $266.70   $266.70  
  7 purchase totals = $702.73       $760.2656   $760.27   $760.30   $760.40