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 $87.39   7.607%   $94.0378   $94.04   $94.05   $94.00  
  Purchase #2 $42.32   13.364%   $47.9756   $47.98   $48.00   $48.00  
  Purchase #3 $104.98   4.857%   $110.0789   $110.08   $110.10   $110.10  
  Purchase #4 $195.50   9.788%   $214.6355   $214.64   $214.65   $214.60  
  Purchase #5 $137.93   3.436%   $142.6693   $142.67   $142.65   $142.70  
  Purchase #6 $149.28   4.564%   $156.0931   $156.09   $156.10   $156.10  
  Purchase #7 $168.31   10.822%   $186.5245   $186.52   $186.50   $186.50  
  7 purchase totals = $885.71       $952.0147   $952.02   $952.05   $952.00