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 $62.49   5.540%   $65.9519   $65.95   $65.95   $66.00  
  Purchase #2 $217.63   7.822%   $234.653   $234.65   $234.65   $234.70  
  Purchase #3 $46.29   12.493%   $52.073   $52.07   $52.05   $52.10  
  Purchase #4 $74.75   3.772%   $77.5696   $77.57   $77.55   $77.60  
  Purchase #5 $85.79   8.372%   $92.9723   $92.97   $92.95   $93.00  
  Purchase #6 $204.31   3.572%   $211.608   $211.61   $211.60   $211.60  
  Purchase #7 $14.46   10.404%   $15.9644   $15.96   $15.95   $16.00  
  7 purchase totals = $705.72       $750.7922   $750.78   $750.70   $751.00