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 $85.78   10.844%   $95.082   $95.08   $95.10   $95.10  
  Purchase #2 $233.99   4.197%   $243.8106   $243.81   $243.80   $243.80  
  Purchase #3 $74.50   10.317%   $82.1862   $82.19   $82.20   $82.20  
  Purchase #4 $91.63   11.871%   $102.5074   $102.51   $102.50   $102.50  
  Purchase #5 $25.70   6.236%   $27.3027   $27.30   $27.30   $27.30  
  Purchase #6 $69.79   5.326%   $73.507   $73.51   $73.50   $73.50  
  Purchase #7 $135.55   6.203%   $143.9582   $143.96   $143.95   $144.00  
  7 purchase totals = $716.94       $768.3541   $768.36   $768.35   $768.40