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 $193.51   4.710%   $202.6243   $202.62   $202.60   $202.60  
  Purchase #2 $162.27   13.774%   $184.6211   $184.62   $184.60   $184.60  
  Purchase #3 $152.64   6.322%   $162.2899   $162.29   $162.30   $162.30  
  Purchase #4 $31.45   8.746%   $34.2006   $34.20   $34.20   $34.20  
  Purchase #5 $45.91   5.186%   $48.2909   $48.29   $48.30   $48.30  
  Purchase #6 $228.73   3.203%   $236.0562   $236.06   $236.05   $236.10  
  Purchase #7 $111.75   13.466%   $126.7983   $126.80   $126.80   $126.80  
  7 purchase totals = $926.26       $994.8813   $994.88   $994.85   $994.90