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 $219.48   8.102%   $237.2623   $237.26   $237.25   $237.30  
  Purchase #2 $231.96   12.807%   $261.6671   $261.67   $261.65   $261.70  
  Purchase #3 $156.78   6.240%   $166.5631   $166.56   $166.55   $166.60  
  Purchase #4 $63.60   4.667%   $66.5682   $66.57   $66.55   $66.60  
  Purchase #5 $194.62   8.591%   $211.3398   $211.34   $211.35   $211.30  
  Purchase #6 $63.35   11.871%   $70.8703   $70.87   $70.85   $70.90  
  Purchase #7 $139.84   12.470%   $157.278   $157.28   $157.30   $157.30  
  7 purchase totals = $1,069.63       $1,171.5488   $1,171.55   $1,171.50   $1,171.70