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 $204.98   4.499%   $214.2021   $214.20   $214.20   $214.20  
  Purchase #2 $13.29   8.635%   $14.4376   $14.44   $14.45   $14.40  
  Purchase #3 $237.36   7.718%   $255.6794   $255.68   $255.70   $255.70  
  Purchase #4 $91.52   7.757%   $98.6192   $98.62   $98.60   $98.60  
  Purchase #5 $105.90   8.510%   $114.9121   $114.91   $114.90   $114.90  
  Purchase #6 $213.31   3.798%   $221.4115   $221.41   $221.40   $221.40  
  Purchase #7 $246.83   8.191%   $267.0478   $267.05   $267.05   $267.00  
  7 purchase totals = $1,113.19       $1,186.3097   $1,186.31   $1,186.30   $1,186.20