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 $162.58   5.800%   $172.0096   $172.01   $172.00   $172.00  
  Purchase #2 $238.95   13.124%   $270.3098   $270.31   $270.30   $270.30  
  Purchase #3 $126.51   3.662%   $131.1428   $131.14   $131.15   $131.10  
  Purchase #4 $70.39   8.481%   $76.3598   $76.36   $76.35   $76.40  
  Purchase #5 $161.47   11.822%   $180.559   $180.56   $180.55   $180.60  
  Purchase #6 $203.91   5.416%   $214.9538   $214.95   $214.95   $215.00  
  Purchase #7 $8.98   5.407%   $9.4655   $9.47   $9.45   $9.50  
  7 purchase totals = $972.79       $1,054.8003   $1,054.80   $1,054.75   $1,054.90