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 $65.54   3.818%   $68.0423   $68.04   $68.05   $68.00  
  Purchase #2 $212.37   3.222%   $219.2126   $219.21   $219.20   $219.20  
  Purchase #3 $211.87   10.175%   $233.4278   $233.43   $233.45   $233.40  
  Purchase #4 $39.48   9.143%   $43.0897   $43.09   $43.10   $43.10  
  Purchase #5 $241.25   10.440%   $266.4365   $266.44   $266.45   $266.40  
  Purchase #6 $215.88   4.420%   $225.4219   $225.42   $225.40   $225.40  
  Purchase #7 $182.82   7.758%   $197.0032   $197.00   $197.00   $197.00  
  7 purchase totals = $1,169.21       $1,252.6340   $1,252.63   $1,252.65   $1,252.50