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 $180.69   7.381%   $194.0267   $194.03   $194.05   $194.00  
  Purchase #2 $67.77   7.259%   $72.6894   $72.69   $72.70   $72.70  
  Purchase #3 $192.86   5.804%   $204.0536   $204.05   $204.05   $204.10  
  Purchase #4 $131.58   3.209%   $135.8024   $135.80   $135.80   $135.80  
  Purchase #5 $196.32   8.633%   $213.2683   $213.27   $213.25   $213.30  
  Purchase #6 $72.93   11.511%   $81.325   $81.33   $81.35   $81.30  
  Purchase #7 $161.51   7.868%   $174.2176   $174.22   $174.20   $174.20  
  7 purchase totals = $1,003.66       $1,075.3830   $1,075.39   $1,075.40   $1,075.40