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 $86.81   9.490%   $95.0483   $95.05   $95.05   $95.00  
  Purchase #2 $82.47   13.442%   $93.5556   $93.56   $93.55   $93.60  
  Purchase #3 $194.97   6.821%   $208.2689   $208.27   $208.25   $208.30  
  Purchase #4 $174.36   3.197%   $179.9343   $179.93   $179.95   $179.90  
  Purchase #5 $233.35   5.844%   $246.987   $246.99   $247.00   $247.00  
  Purchase #6 $237.96   11.583%   $265.5229   $265.52   $265.50   $265.50  
  Purchase #7 $244.66   9.538%   $267.9957   $268.00   $268.00   $268.00  
  7 purchase totals = $1,254.58       $1,357.3127   $1,357.32   $1,357.30   $1,357.30