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 $60.39   8.125%   $65.2967   $65.30   $65.30   $65.30  
  Purchase #2 $206.36   10.331%   $227.6791   $227.68   $227.70   $227.70  
  Purchase #3 $171.37   7.547%   $184.3033   $184.30   $184.30   $184.30  
  Purchase #4 $106.75   13.452%   $121.11   $121.11   $121.10   $121.10  
  Purchase #5 $214.41   9.190%   $234.1143   $234.11   $234.10   $234.10  
  Purchase #6 $15.77   7.411%   $16.9387   $16.94   $16.95   $16.90  
  Purchase #7 $244.77   7.108%   $262.1683   $262.17   $262.15   $262.20  
  7 purchase totals = $1,019.82       $1,111.6104   $1,111.61   $1,111.60   $1,111.60