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 $179.30   10.235%   $197.6514   $197.65   $197.65   $197.70  
  Purchase #2 $115.52   5.851%   $122.2791   $122.28   $122.30   $122.30  
  Purchase #3 $40.67   13.844%   $46.3004   $46.30   $46.30   $46.30  
  Purchase #4 $116.66   13.596%   $132.5211   $132.52   $132.50   $132.50  
  Purchase #5 $77.85   11.624%   $86.8993   $86.90   $86.90   $86.90  
  Purchase #6 $216.65   10.365%   $239.1058   $239.11   $239.10   $239.10  
  Purchase #7 $183.82   9.694%   $201.6395   $201.64   $201.65   $201.60  
  7 purchase totals = $930.47       $1,026.3966   $1,026.40   $1,026.40   $1,026.40