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 $173.75   12.619%   $195.6755   $195.68   $195.70   $195.70  
  Purchase #2 $186.48   13.613%   $211.8655   $211.87   $211.85   $211.90  
  Purchase #3 $245.92   7.197%   $263.6189   $263.62   $263.60   $263.60  
  Purchase #4 $134.34   13.574%   $152.5753   $152.58   $152.60   $152.60  
  Purchase #5 $184.45   4.782%   $193.2704   $193.27   $193.25   $193.30  
  Purchase #6 $147.81   13.821%   $168.2388   $168.24   $168.25   $168.20  
  Purchase #7 $225.44   8.318%   $244.1921   $244.19   $244.20   $244.20  
  7 purchase totals = $1,298.19       $1,429.4365   $1,429.45   $1,429.45   $1,429.50