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 $96.41   11.868%   $107.8519   $107.85   $107.85   $107.90  
  Purchase #2 $158.47   12.168%   $177.7526   $177.75   $177.75   $177.80  
  Purchase #3 $184.53   5.683%   $195.0168   $195.02   $195.00   $195.00  
  Purchase #4 $214.69   7.206%   $230.1606   $230.16   $230.15   $230.20  
  Purchase #5 $49.85   7.148%   $53.4133   $53.41   $53.40   $53.40  
  Purchase #6 $62.91   11.355%   $70.0534   $70.05   $70.05   $70.10  
  Purchase #7 $86.79   13.663%   $98.6481   $98.65   $98.65   $98.60  
  7 purchase totals = $853.65       $932.8967   $932.89   $932.85   $933.00