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 $176.46   11.218%   $196.2553   $196.26   $196.25   $196.30  
  Purchase #2 $154.58   4.444%   $161.4495   $161.45   $161.45   $161.40  
  Purchase #3 $170.39   3.653%   $176.6143   $176.61   $176.60   $176.60  
  Purchase #4 $209.73   11.334%   $233.5008   $233.50   $233.50   $233.50  
  Purchase #5 $204.41   8.286%   $221.3474   $221.35   $221.35   $221.30  
  Purchase #6 $118.32   6.536%   $126.0534   $126.05   $126.05   $126.10  
  Purchase #7 $100.61   4.534%   $105.1717   $105.17   $105.15   $105.20  
  7 purchase totals = $1,134.50       $1,220.3924   $1,220.39   $1,220.35   $1,220.40