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 $22.25   11.612%   $24.8337   $24.83   $24.85   $24.80  
  Purchase #2 $167.26   10.279%   $184.4527   $184.45   $184.45   $184.50  
  Purchase #3 $126.45   6.654%   $134.864   $134.86   $134.85   $134.90  
  Purchase #4 $231.32   6.280%   $245.8469   $245.85   $245.85   $245.80  
  Purchase #5 $215.55   11.173%   $239.6334   $239.63   $239.65   $239.60  
  Purchase #6 $134.79   12.594%   $151.7655   $151.77   $151.75   $151.80  
  Purchase #7 $186.64   9.375%   $204.1375   $204.14   $204.15   $204.10  
  7 purchase totals = $1,084.26       $1,185.5337   $1,185.53   $1,185.55   $1,185.50