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 $47.33   10.598%   $52.346   $52.35   $52.35   $52.30  
  Purchase #2 $241.96   10.481%   $267.3198   $267.32   $267.30   $267.30  
  Purchase #3 $208.94   11.862%   $233.7245   $233.72   $233.70   $233.70  
  Purchase #4 $239.44   11.346%   $266.6069   $266.61   $266.60   $266.60  
  Purchase #5 $56.65   5.305%   $59.6553   $59.66   $59.65   $59.70  
  Purchase #6 $31.90   11.418%   $35.5423   $35.54   $35.55   $35.50  
  Purchase #7 $68.99   11.739%   $77.0887   $77.09   $77.10   $77.10  
  7 purchase totals = $895.21       $992.2835   $992.29   $992.25   $992.20