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 $69.71   10.715%   $77.1794   $77.18   $77.20   $77.20  
  Purchase #2 $186.52   4.390%   $194.7082   $194.71   $194.70   $194.70  
  Purchase #3 $204.69   13.638%   $232.6056   $232.61   $232.60   $232.60  
  Purchase #4 $96.78   10.225%   $106.6758   $106.68   $106.70   $106.70  
  Purchase #5 $194.88   3.396%   $201.4981   $201.50   $201.50   $201.50  
  Purchase #6 $239.59   10.367%   $264.4283   $264.43   $264.45   $264.40  
  Purchase #7 $170.42   7.658%   $183.4708   $183.47   $183.45   $183.50  
  7 purchase totals = $1,162.59       $1,260.5662   $1,260.58   $1,260.60   $1,260.60