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	$223.70	9.134%	$244.1328	$244.13	$244.15	$244.10
Purchase #2	$46.74	5.811%	$49.4561	$49.46	$49.45	$49.50
Purchase #3	$241.27	10.469%	$266.5286	$266.53	$266.55	$266.50
Purchase #4	$38.33	5.117%	$40.2913	$40.29	$40.30	$40.30
Purchase #5	$210.81	12.708%	$237.5997	$237.60	$237.60	$237.60
Purchase #6	$123.52	3.124%	$127.3788	$127.38	$127.40	$127.40
Purchase #7	$25.46	11.743%	$28.4498	$28.45	$28.45	$28.40
7 purchase totals =	$909.83		$993.8371	$993.84	$993.90	$993.80