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 $161.73   4.873%   $169.6111   $169.61   $169.60   $169.60  
  Purchase #2 $221.61   8.466%   $240.3715   $240.37   $240.35   $240.40  
  Purchase #3 $248.50   8.320%   $269.1752   $269.18   $269.20   $269.20  
  Purchase #4 $63.58   3.243%   $65.6419   $65.64   $65.65   $65.60  
  Purchase #5 $128.37   3.770%   $133.2095   $133.21   $133.20   $133.20  
  Purchase #6 $54.88   8.434%   $59.5086   $59.51   $59.50   $59.50  
  Purchase #7 $216.62   8.712%   $235.4919   $235.49   $235.50   $235.50  
  7 purchase totals = $1,095.29       $1,173.0097   $1,173.01   $1,173.00   $1,173.00