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 $158.63   11.325%   $176.5948   $176.59   $176.60   $176.60  
  Purchase #2 $31.31   4.347%   $32.671   $32.67   $32.65   $32.70  
  Purchase #3 $116.77   6.116%   $123.9117   $123.91   $123.90   $123.90  
  Purchase #4 $197.50   5.161%   $207.693   $207.69   $207.70   $207.70  
  Purchase #5 $114.78   5.223%   $120.775   $120.78   $120.80   $120.80  
  Purchase #6 $196.53   4.276%   $204.9336   $204.93   $204.95   $204.90  
  Purchase #7 $240.68   12.155%   $269.9347   $269.93   $269.95   $269.90  
  7 purchase totals = $1,056.20       $1,136.5138   $1,136.50   $1,136.55   $1,136.50