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 $161.32   8.262%   $174.6483   $174.65   $174.65   $174.60  
  Purchase #2 $112.69   11.848%   $126.0415   $126.04   $126.05   $126.00  
  Purchase #3 $22.32   8.659%   $24.2527   $24.25   $24.25   $24.30  
  Purchase #4 $160.82   4.568%   $168.1663   $168.17   $168.15   $168.20  
  Purchase #5 $84.41   4.608%   $88.2996   $88.30   $88.30   $88.30  
  Purchase #6 $208.57   4.460%   $217.8722   $217.87   $217.85   $217.90  
  Purchase #7 $211.32   10.466%   $233.4368   $233.44   $233.45   $233.40  
  7 purchase totals = $961.45       $1,032.7174   $1,032.72   $1,032.70   $1,032.70