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	$249.70	6.786%	$266.6446	$266.64	$266.65	$266.60
Purchase #2	$36.80	5.473%	$38.8141	$38.81	$38.80	$38.80
Purchase #3	$242.88	4.414%	$253.6007	$253.60	$253.60	$253.60
Purchase #4	$80.54	10.697%	$89.1554	$89.16	$89.15	$89.20
Purchase #5	$114.54	11.354%	$127.5449	$127.54	$127.55	$127.50
Purchase #6	$101.68	4.738%	$106.4976	$106.50	$106.50	$106.50
Purchase #7	$206.92	12.741%	$233.2837	$233.28	$233.30	$233.30
7 purchase totals =	$1,033.06		$1,115.5410	$1,115.53	$1,115.55	$1,115.50