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 $114.50   4.463%   $119.6101   $119.61   $119.60   $119.60  
  Purchase #2 $88.46   9.320%   $96.7045   $96.70   $96.70   $96.70  
  Purchase #3 $206.96   8.177%   $223.8831   $223.88   $223.90   $223.90  
  Purchase #4 $211.60   8.249%   $229.0549   $229.05   $229.05   $229.10  
  Purchase #5 $84.37   13.696%   $95.9253   $95.93   $95.95   $95.90  
  Purchase #6 $241.60   11.855%   $270.2417   $270.24   $270.25   $270.20  
  Purchase #7 $135.50   4.495%   $141.5907   $141.59   $141.60   $141.60  
  7 purchase totals = $1,082.99       $1,177.0103   $1,177.00   $1,177.05   $1,177.00