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 $55.65   10.512%   $61.4999   $61.50   $61.50   $61.50  
  Purchase #2 $153.64   6.218%   $163.1933   $163.19   $163.20   $163.20  
  Purchase #3 $230.31   13.854%   $262.2171   $262.22   $262.20   $262.20  
  Purchase #4 $180.30   6.576%   $192.1565   $192.16   $192.15   $192.20  
  Purchase #5 $64.74   3.430%   $66.9606   $66.96   $66.95   $67.00  
  Purchase #6 $227.59   9.334%   $248.8333   $248.83   $248.85   $248.80  
  Purchase #7 $60.90   3.429%   $62.9883   $62.99   $63.00   $63.00  
  7 purchase totals = $973.13       $1,057.8490   $1,057.85   $1,057.85   $1,057.90