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 $186.54   10.617%   $206.345   $206.35   $206.35   $206.30  
  Purchase #2 $201.76   7.677%   $217.2491   $217.25   $217.25   $217.20  
  Purchase #3 $48.72   12.822%   $54.9669   $54.97   $54.95   $55.00  
  Purchase #4 $178.85   9.565%   $195.957   $195.96   $195.95   $196.00  
  Purchase #5 $216.27   5.235%   $227.5917   $227.59   $227.60   $227.60  
  Purchase #6 $158.76   12.197%   $178.124   $178.12   $178.10   $178.10  
  Purchase #7 $80.45   9.727%   $88.2754   $88.28   $88.30   $88.30  
  7 purchase totals = $1,071.35       $1,168.5091   $1,168.52   $1,168.50   $1,168.50