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 $56.28   10.671%   $62.2856   $62.29   $62.30   $62.30  
  Purchase #2 $139.96   7.613%   $150.6152   $150.62   $150.60   $150.60  
  Purchase #3 $70.34   5.215%   $74.0082   $74.01   $74.00   $74.00  
  Purchase #4 $152.86   6.854%   $163.337   $163.34   $163.35   $163.30  
  Purchase #5 $106.84   13.672%   $121.4472   $121.45   $121.45   $121.40  
  Purchase #6 $133.70   7.670%   $143.9548   $143.95   $143.95   $144.00  
  Purchase #7 $43.95   10.809%   $48.7006   $48.70   $48.70   $48.70  
  7 purchase totals = $703.93       $764.3486   $764.36   $764.35   $764.30