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	$62.57	8.223%	$67.7151	$67.72	$67.70	$67.70
Purchase #2	$105.75	3.730%	$109.6945	$109.69	$109.70	$109.70
Purchase #3	$67.35	10.141%	$74.18	$74.18	$74.20	$74.20
Purchase #4	$131.42	12.123%	$147.352	$147.35	$147.35	$147.40
Purchase #5	$158.78	4.758%	$166.3348	$166.33	$166.35	$166.30
Purchase #6	$115.29	10.486%	$127.3793	$127.38	$127.40	$127.40
Purchase #7	$235.86	9.326%	$257.8563	$257.86	$257.85	$257.90
7 purchase totals =	$877.02		$950.5120	$950.51	$950.55	$950.60