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 $207.43   3.146%   $213.9557   $213.96   $213.95   $214.00  
  Purchase #2 $220.78   11.120%   $245.3307   $245.33   $245.35   $245.30  
  Purchase #3 $77.48   11.182%   $86.1438   $86.14   $86.15   $86.10  
  Purchase #4 $202.32   10.824%   $224.2191   $224.22   $224.20   $224.20  
  Purchase #5 $249.64   6.514%   $265.9015   $265.90   $265.90   $265.90  
  Purchase #6 $205.98   6.225%   $218.8023   $218.80   $218.80   $218.80  
  Purchase #7 $141.95   11.678%   $158.5269   $158.53   $158.55   $158.50  
  7 purchase totals = $1,305.58       $1,412.8800   $1,412.88   $1,412.90   $1,412.80