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 $177.92   10.573%   $196.7315   $196.73   $196.75   $196.70  
  Purchase #2 $202.71   7.574%   $218.0633   $218.06   $218.05   $218.10  
  Purchase #3 $230.89   11.119%   $256.5627   $256.56   $256.55   $256.60  
  Purchase #4 $184.36   6.762%   $196.8264   $196.83   $196.85   $196.80  
  Purchase #5 $106.99   11.849%   $119.6672   $119.67   $119.65   $119.70  
  Purchase #6 $230.97   9.554%   $253.0369   $253.04   $253.05   $253.00  
  Purchase #7 $215.26   12.772%   $242.753   $242.75   $242.75   $242.80  
  7 purchase totals = $1,349.10       $1,483.6410   $1,483.64   $1,483.65   $1,483.70