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	$174.83	12.508%	$196.6977	$196.70	$196.70	$196.70
Purchase #2	$69.63	3.615%	$72.1471	$72.15	$72.15	$72.10
Purchase #3	$45.33	5.140%	$47.66	$47.66	$47.65	$47.70
Purchase #4	$46.99	6.572%	$50.0782	$50.08	$50.10	$50.10
Purchase #5	$118.70	13.549%	$134.7827	$134.78	$134.80	$134.80
Purchase #6	$107.56	4.637%	$112.5476	$112.55	$112.55	$112.50
Purchase #7	$43.58	4.848%	$45.6928	$45.69	$45.70	$45.70
7 purchase totals =	$606.62		$659.6061	$659.61	$659.65	$659.60