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 $195.83   11.339%   $218.0352   $218.04   $218.05   $218.00  
  Purchase #2 $157.34   4.235%   $164.0033   $164.00   $164.00   $164.00  
  Purchase #3 $144.48   6.617%   $154.0402   $154.04   $154.05   $154.00  
  Purchase #4 $224.81   7.435%   $241.5246   $241.52   $241.50   $241.50  
  Purchase #5 $200.51   13.168%   $226.9132   $226.91   $226.90   $226.90  
  Purchase #6 $49.62   12.107%   $55.6275   $55.63   $55.65   $55.60  
  Purchase #7 $212.83   10.373%   $234.9069   $234.91   $234.90   $234.90  
  7 purchase totals = $1,185.42       $1,295.0509   $1,295.05   $1,295.05   $1,294.90