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 $59.37   5.509%   $62.6407   $62.64   $62.65   $62.60  
  Purchase #2 $154.32   4.549%   $161.34   $161.34   $161.35   $161.30  
  Purchase #3 $180.41   11.699%   $201.5162   $201.52   $201.50   $201.50  
  Purchase #4 $213.67   5.846%   $226.1611   $226.16   $226.15   $226.20  
  Purchase #5 $140.67   8.107%   $152.0741   $152.07   $152.05   $152.10  
  Purchase #6 $42.49   9.526%   $46.5376   $46.54   $46.55   $46.50  
  Purchase #7 $64.25   8.585%   $69.7659   $69.77   $69.75   $69.80  
  7 purchase totals = $855.18       $920.0356   $920.04   $920.00   $920.00