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 $57.95   6.861%   $61.9259   $61.93   $61.95   $61.90  
  Purchase #2 $164.52   5.833%   $174.1165   $174.12   $174.10   $174.10  
  Purchase #3 $214.79   11.687%   $239.8925   $239.89   $239.90   $239.90  
  Purchase #4 $80.96   11.677%   $90.4137   $90.41   $90.40   $90.40  
  Purchase #5 $112.94   10.373%   $124.6553   $124.66   $124.65   $124.70  
  Purchase #6 $193.88   6.723%   $206.9146   $206.91   $206.90   $206.90  
  Purchase #7 $216.35   11.599%   $241.4444   $241.44   $241.45   $241.40  
  7 purchase totals = $1,041.39       $1,139.3629   $1,139.36   $1,139.35   $1,139.30