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 $61.87   3.735%   $64.1808   $64.18   $64.20   $64.20  
  Purchase #2 $168.67   10.704%   $186.7244   $186.72   $186.70   $186.70  
  Purchase #3 $33.48   11.346%   $37.2786   $37.28   $37.30   $37.30  
  Purchase #4 $153.93   11.465%   $171.5781   $171.58   $171.60   $171.60  
  Purchase #5 $166.85   7.578%   $179.4939   $179.49   $179.50   $179.50  
  Purchase #6 $207.99   13.241%   $235.53   $235.53   $235.55   $235.50  
  Purchase #7 $137.29   10.179%   $151.2647   $151.26   $151.25   $151.30  
  7 purchase totals = $930.08       $1,026.0505   $1,026.04   $1,026.10   $1,026.10