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 $181.95   10.746%   $201.5023   $201.50   $201.50   $201.50  
  Purchase #2 $233.30   13.422%   $264.6135   $264.61   $264.60   $264.60  
  Purchase #3 $74.84   10.468%   $82.6743   $82.67   $82.65   $82.70  
  Purchase #4 $208.27   11.352%   $231.9128   $231.91   $231.90   $231.90  
  Purchase #5 $111.37   5.119%   $117.071   $117.07   $117.05   $117.10  
  Purchase #6 $69.78   9.862%   $76.6617   $76.66   $76.65   $76.70  
  Purchase #7 $81.34   5.853%   $86.1008   $86.10   $86.10   $86.10  
  7 purchase totals = $960.85       $1,060.5364   $1,060.52   $1,060.45   $1,060.60