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 $161.72   13.805%   $184.0454   $184.05   $184.05   $184.00  
  Purchase #2 $26.63   3.417%   $27.5399   $27.54   $27.55   $27.50  
  Purchase #3 $245.63   11.241%   $273.2413   $273.24   $273.25   $273.20  
  Purchase #4 $80.68   13.355%   $91.4548   $91.45   $91.45   $91.50  
  Purchase #5 $228.68   5.620%   $241.5318   $241.53   $241.55   $241.50  
  Purchase #6 $220.93   12.512%   $248.5728   $248.57   $248.55   $248.60  
  Purchase #7 $27.83   5.776%   $29.4375   $29.44   $29.45   $29.40  
  7 purchase totals = $992.10       $1,095.8235   $1,095.82   $1,095.85   $1,095.70