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 $176.71   11.814%   $197.5865   $197.59   $197.60   $197.60  
  Purchase #2 $46.63   12.162%   $52.3011   $52.30   $52.30   $52.30  
  Purchase #3 $126.72   6.756%   $135.2812   $135.28   $135.30   $135.30  
  Purchase #4 $50.95   8.528%   $55.295   $55.30   $55.30   $55.30  
  Purchase #5 $243.68   13.169%   $275.7702   $275.77   $275.75   $275.80  
  Purchase #6 $92.35   10.546%   $102.0892   $102.09   $102.10   $102.10  
  Purchase #7 $244.63   5.322%   $257.6492   $257.65   $257.65   $257.60  
  7 purchase totals = $981.67       $1,075.9724   $1,075.98   $1,076.00   $1,076.00