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	$232.91	3.346%	$240.7032	$240.70	$240.70	$240.70
Purchase #2	$10.82	7.845%	$11.6688	$11.67	$11.65	$11.70
Purchase #3	$142.74	3.736%	$148.0728	$148.07	$148.05	$148.10
Purchase #4	$212.72	5.170%	$223.7176	$223.72	$223.70	$223.70
Purchase #5	$170.60	4.730%	$178.6694	$178.67	$178.65	$178.70
Purchase #6	$35.87	3.233%	$37.0297	$37.03	$37.05	$37.00
Purchase #7	$161.59	10.448%	$178.4729	$178.47	$178.45	$178.50
7 purchase totals =	$967.25		$1,018.3344	$1,018.33	$1,018.25	$1,018.40