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 $24.34   7.722%   $26.2195   $26.22   $26.20   $26.20  
  Purchase #2 $60.88   6.699%   $64.9584   $64.96   $64.95   $65.00  
  Purchase #3 $98.37   3.298%   $101.6142   $101.61   $101.60   $101.60  
  Purchase #4 $213.73   9.490%   $234.013   $234.01   $234.00   $234.00  
  Purchase #5 $171.52   8.738%   $186.5074   $186.51   $186.50   $186.50  
  Purchase #6 $193.93   3.829%   $201.3556   $201.36   $201.35   $201.40  
  Purchase #7 $228.58   8.420%   $247.8264   $247.83   $247.85   $247.80  
  7 purchase totals = $991.35       $1,062.4945   $1,062.50   $1,062.45   $1,062.50