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	$152.31	5.402%	$160.5378	$160.54	$160.55	$160.50
Purchase #2	$66.86	5.428%	$70.4892	$70.49	$70.50	$70.50
Purchase #3	$114.80	10.714%	$127.0997	$127.10	$127.10	$127.10
Purchase #4	$97.58	3.233%	$100.7348	$100.73	$100.75	$100.70
Purchase #5	$62.57	4.316%	$65.2705	$65.27	$65.25	$65.30
Purchase #6	$150.65	3.491%	$155.9092	$155.91	$155.90	$155.90
Purchase #7	$196.66	8.625%	$213.6219	$213.62	$213.60	$213.60
7 purchase totals =	$841.43		$893.6631	$893.66	$893.65	$893.60