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 $194.32   3.590%   $201.2961   $201.30   $201.30   $201.30  
  Purchase #2 $212.95   11.405%   $237.2369   $237.24   $237.25   $237.20  
  Purchase #3 $53.39   5.621%   $56.3911   $56.39   $56.40   $56.40  
  Purchase #4 $174.63   4.119%   $181.823   $181.82   $181.80   $181.80  
  Purchase #5 $215.47   6.854%   $230.2383   $230.24   $230.25   $230.20  
  Purchase #6 $103.67   13.412%   $117.5742   $117.57   $117.55   $117.60  
  Purchase #7 $120.68   12.773%   $136.0945   $136.09   $136.10   $136.10  
  7 purchase totals = $1,075.11       $1,160.6541   $1,160.65   $1,160.65   $1,160.60