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 $191.85   5.516%   $202.4324   $202.43   $202.45   $202.40  
  Purchase #2 $136.99   7.354%   $147.0642   $147.06   $147.05   $147.10  
  Purchase #3 $239.34   13.483%   $271.6102   $271.61   $271.60   $271.60  
  Purchase #4 $223.39   9.802%   $245.2867   $245.29   $245.30   $245.30  
  Purchase #5 $58.70   9.428%   $64.2342   $64.23   $64.25   $64.20  
  Purchase #6 $193.89   3.535%   $200.744   $200.74   $200.75   $200.70  
  Purchase #7 $222.91   9.724%   $244.5858   $244.59   $244.60   $244.60  
  7 purchase totals = $1,267.07       $1,375.9575   $1,375.95   $1,376.00   $1,375.90