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	$249.58	6.853%	$266.6837	$266.68	$266.70	$266.70
Purchase #2	$153.56	10.460%	$169.6224	$169.62	$169.60	$169.60
Purchase #3	$155.94	6.121%	$165.4851	$165.49	$165.50	$165.50
Purchase #4	$205.78	8.622%	$223.5224	$223.52	$223.50	$223.50
Purchase #5	$104.58	9.444%	$114.4565	$114.46	$114.45	$114.50
Purchase #6	$88.45	3.779%	$91.7925	$91.79	$91.80	$91.80
Purchase #7	$126.88	8.347%	$137.4707	$137.47	$137.45	$137.50
7 purchase totals =	$1,084.77		$1,169.0333	$1,169.03	$1,169.00	$1,169.10