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	$241.36	5.692%	$255.0982	$255.10	$255.10	$255.10
Purchase #2	$200.51	3.385%	$207.2973	$207.30	$207.30	$207.30
Purchase #3	$194.58	10.590%	$215.186	$215.19	$215.20	$215.20
Purchase #4	$30.27	4.271%	$31.5628	$31.56	$31.55	$31.60
Purchase #5	$100.73	12.105%	$112.9234	$112.92	$112.90	$112.90
Purchase #6	$57.76	6.478%	$61.5017	$61.50	$61.50	$61.50
Purchase #7	$174.53	9.196%	$190.5798	$190.58	$190.60	$190.60
7 purchase totals =	$999.74		$1,074.1492	$1,074.15	$1,074.15	$1,074.20