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 $58.58   4.165%   $61.0199   $61.02   $61.00   $61.00  
  Purchase #2 $114.75   13.489%   $130.2286   $130.23   $130.25   $130.20  
  Purchase #3 $208.82   9.413%   $228.4762   $228.48   $228.50   $228.50  
  Purchase #4 $151.68   8.119%   $163.9949   $163.99   $164.00   $164.00  
  Purchase #5 $120.82   8.179%   $130.7019   $130.70   $130.70   $130.70  
  Purchase #6 $241.30   9.483%   $264.1825   $264.18   $264.20   $264.20  
  Purchase #7 $134.99   12.628%   $152.0365   $152.04   $152.05   $152.00  
  7 purchase totals = $1,030.94       $1,130.6405   $1,130.64   $1,130.70   $1,130.60