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 $43.81   8.362%   $47.4734   $47.47   $47.45   $47.50  
  Purchase #2 $194.77   7.282%   $208.9532   $208.95   $208.95   $209.00  
  Purchase #3 $55.40   11.871%   $61.9765   $61.98   $62.00   $62.00  
  Purchase #4 $227.97   8.766%   $247.9539   $247.95   $247.95   $248.00  
  Purchase #5 $218.62   7.397%   $234.7913   $234.79   $234.80   $234.80  
  Purchase #6 $200.41   12.659%   $225.7799   $225.78   $225.80   $225.80  
  Purchase #7 $39.94   5.176%   $42.0073   $42.01   $42.00   $42.00  
  7 purchase totals = $980.92       $1,068.9355   $1,068.93   $1,068.95   $1,069.10