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	$179.26	10.809%	$198.6362	$198.64	$198.65	$198.60
Purchase #2	$162.94	12.577%	$183.433	$183.43	$183.45	$183.40
Purchase #3	$62.52	4.823%	$65.5353	$65.54	$65.55	$65.50
Purchase #4	$239.43	11.158%	$266.1456	$266.15	$266.15	$266.10
Purchase #5	$209.82	13.681%	$238.5255	$238.53	$238.55	$238.50
Purchase #6	$210.61	13.167%	$238.341	$238.34	$238.35	$238.30
Purchase #7	$177.70	4.170%	$185.1101	$185.11	$185.10	$185.10
7 purchase totals =	$1,242.28		$1,375.7267	$1,375.74	$1,375.80	$1,375.50