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 $46.31   5.305%   $48.7667   $48.77   $48.75   $48.80  
  Purchase #2 $59.72   4.838%   $62.6093   $62.61   $62.60   $62.60  
  Purchase #3 $212.99   12.310%   $239.2091   $239.21   $239.20   $239.20  
  Purchase #4 $171.61   6.198%   $182.2464   $182.25   $182.25   $182.20  
  Purchase #5 $189.64   4.418%   $198.0183   $198.02   $198.00   $198.00  
  Purchase #6 $178.27   4.709%   $186.6647   $186.66   $186.65   $186.70  
  Purchase #7 $115.48   7.399%   $124.0244   $124.02   $124.00   $124.00  
  7 purchase totals = $974.02       $1,041.5389   $1,041.54   $1,041.45   $1,041.50