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 $201.83   5.808%   $213.5523   $213.55   $213.55   $213.60  
  Purchase #2 $114.51   3.728%   $118.7789   $118.78   $118.80   $118.80  
  Purchase #3 $211.97   5.493%   $223.6135   $223.61   $223.60   $223.60  
  Purchase #4 $112.90   8.245%   $122.2086   $122.21   $122.20   $122.20  
  Purchase #5 $69.41   3.554%   $71.8768   $71.88   $71.90   $71.90  
  Purchase #6 $226.40   7.865%   $244.2064   $244.21   $244.20   $244.20  
  Purchase #7 $10.63   3.155%   $10.9654   $10.97   $10.95   $11.00  
  7 purchase totals = $947.65       $1,005.2019   $1,005.21   $1,005.20   $1,005.30