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 $56.44   10.608%   $62.4272   $62.43   $62.45   $62.40  
  Purchase #2 $195.38   10.486%   $215.8675   $215.87   $215.85   $215.90  
  Purchase #3 $97.45   11.361%   $108.5213   $108.52   $108.50   $108.50  
  Purchase #4 $57.45   5.404%   $60.5546   $60.55   $60.55   $60.60  
  Purchase #5 $166.93   9.720%   $183.1556   $183.16   $183.15   $183.20  
  Purchase #6 $208.49   6.717%   $222.4943   $222.49   $222.50   $222.50  
  Purchase #7 $187.37   6.733%   $199.9856   $199.99   $200.00   $200.00  
  7 purchase totals = $969.51       $1,053.0061   $1,053.01   $1,053.00   $1,053.10