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 $178.91   12.366%   $201.034   $201.03   $201.05   $201.00  
  Purchase #2 $84.68   10.542%   $93.607   $93.61   $93.60   $93.60  
  Purchase #3 $185.26   7.740%   $199.5991   $199.60   $199.60   $199.60  
  Purchase #4 $136.77   10.469%   $151.0885   $151.09   $151.10   $151.10  
  Purchase #5 $89.85   7.582%   $96.6624   $96.66   $96.65   $96.70  
  Purchase #6 $234.81   13.299%   $266.0374   $266.04   $266.05   $266.00  
  Purchase #7 $149.91   4.614%   $156.8268   $156.83   $156.85   $156.80  
  7 purchase totals = $1,060.19       $1,164.8552   $1,164.86   $1,164.90   $1,164.80