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 $194.77   3.697%   $201.9706   $201.97   $201.95   $202.00  
  Purchase #2 $76.26   5.523%   $80.4718   $80.47   $80.45   $80.50  
  Purchase #3 $131.42   11.870%   $147.0196   $147.02   $147.00   $147.00  
  Purchase #4 $192.71   9.537%   $211.0888   $211.09   $211.10   $211.10  
  Purchase #5 $247.80   11.229%   $275.6255   $275.63   $275.65   $275.60  
  Purchase #6 $6.76   10.579%   $7.4751   $7.48   $7.50   $7.50  
  Purchase #7 $164.73   11.145%   $183.0892   $183.09   $183.10   $183.10  
  7 purchase totals = $1,014.45       $1,106.7406   $1,106.75   $1,106.75   $1,106.80