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 $181.90   8.269%   $196.9413   $196.94   $196.95   $196.90  
  Purchase #2 $24.94   4.400%   $26.0374   $26.04   $26.05   $26.00  
  Purchase #3 $199.37   7.318%   $213.9599   $213.96   $213.95   $214.00  
  Purchase #4 $169.37   5.628%   $178.9021   $178.90   $178.90   $178.90  
  Purchase #5 $102.71   12.623%   $115.6751   $115.68   $115.70   $115.70  
  Purchase #6 $234.74   10.710%   $259.8807   $259.88   $259.90   $259.90  
  Purchase #7 $150.62   11.620%   $168.122   $168.12   $168.10   $168.10  
  7 purchase totals = $1,063.65       $1,159.5185   $1,159.52   $1,159.55   $1,159.50