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 $60.69   4.851%   $63.6341   $63.63   $63.65   $63.60  
  Purchase #2 $204.90   3.337%   $211.7375   $211.74   $211.75   $211.70  
  Purchase #3 $47.34   7.371%   $50.8294   $50.83   $50.85   $50.80  
  Purchase #4 $208.69   13.251%   $236.3435   $236.34   $236.35   $236.30  
  Purchase #5 $88.56   5.390%   $93.3334   $93.33   $93.35   $93.30  
  Purchase #6 $243.62   5.313%   $256.5635   $256.56   $256.55   $256.60  
  Purchase #7 $177.79   3.854%   $184.642   $184.64   $184.65   $184.60  
  7 purchase totals = $1,031.59       $1,097.0834   $1,097.07   $1,097.15   $1,096.90