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 $61.27   4.398%   $63.9647   $63.96   $63.95   $64.00  
  Purchase #2 $19.25   12.348%   $21.627   $21.63   $21.65   $21.60  
  Purchase #3 $219.77   12.114%   $246.3929   $246.39   $246.40   $246.40  
  Purchase #4 $101.72   5.789%   $107.6086   $107.61   $107.60   $107.60  
  Purchase #5 $173.51   3.667%   $179.8726   $179.87   $179.85   $179.90  
  Purchase #6 $201.43   7.348%   $216.2311   $216.23   $216.25   $216.20  
  Purchase #7 $195.47   6.673%   $208.5137   $208.51   $208.50   $208.50  
  7 purchase totals = $972.42       $1,044.2106   $1,044.20   $1,044.20   $1,044.20