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 $201.50   5.602%   $212.788   $212.79   $212.80   $212.80  
  Purchase #2 $194.43   9.857%   $213.595   $213.60   $213.60   $213.60  
  Purchase #3 $67.78   6.245%   $72.0129   $72.01   $72.00   $72.00  
  Purchase #4 $163.57   8.778%   $177.9282   $177.93   $177.95   $177.90  
  Purchase #5 $87.41   10.444%   $96.5391   $96.54   $96.55   $96.50  
  Purchase #6 $33.43   11.589%   $37.3042   $37.30   $37.30   $37.30  
  Purchase #7 $169.55   9.247%   $185.2283   $185.23   $185.25   $185.20  
  7 purchase totals = $917.67       $995.3957   $995.40   $995.45   $995.30