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 $62.69   4.804%   $65.7016   $65.70   $65.70   $65.70  
  Purchase #2 $228.63   3.398%   $236.3988   $236.40   $236.40   $236.40  
  Purchase #3 $88.96   8.318%   $96.3597   $96.36   $96.35   $96.40  
  Purchase #4 $226.70   3.301%   $234.1834   $234.18   $234.20   $234.20  
  Purchase #5 $233.60   8.227%   $252.8183   $252.82   $252.80   $252.80  
  Purchase #6 $181.81   12.473%   $204.4872   $204.49   $204.50   $204.50  
  Purchase #7 $80.81   12.571%   $90.9686   $90.97   $90.95   $91.00  
  7 purchase totals = $1,103.20       $1,180.9176   $1,180.92   $1,180.90   $1,181.00