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 $114.58   4.465%   $119.696   $119.70   $119.70   $119.70  
  Purchase #2 $32.95   6.847%   $35.2061   $35.21   $35.20   $35.20  
  Purchase #3 $49.84   7.689%   $53.6722   $53.67   $53.65   $53.70  
  Purchase #4 $41.31   7.704%   $44.4925   $44.49   $44.50   $44.50  
  Purchase #5 $225.26   4.493%   $235.3809   $235.38   $235.40   $235.40  
  Purchase #6 $177.82   10.812%   $197.0459   $197.05   $197.05   $197.00  
  Purchase #7 $226.57   8.779%   $246.4606   $246.46   $246.45   $246.50  
  7 purchase totals = $868.33       $931.9542   $931.96   $931.95   $932.00