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 $43.87   9.338%   $47.9666   $47.97   $47.95   $48.00  
  Purchase #2 $92.75   13.476%   $105.249   $105.25   $105.25   $105.20  
  Purchase #3 $33.44   11.493%   $37.2833   $37.28   $37.30   $37.30  
  Purchase #4 $237.55   3.320%   $245.4367   $245.44   $245.45   $245.40  
  Purchase #5 $169.52   4.470%   $177.0975   $177.10   $177.10   $177.10  
  Purchase #6 $149.49   3.205%   $154.2812   $154.28   $154.30   $154.30  
  Purchase #7 $238.70   11.387%   $265.8808   $265.88   $265.90   $265.90  
  7 purchase totals = $965.32       $1,033.1951   $1,033.20   $1,033.25   $1,033.20