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	$161.41	9.699%	$177.0652	$177.07	$177.05	$177.10
Purchase #2	$144.72	4.501%	$151.2338	$151.23	$151.25	$151.20
Purchase #3	$30.45	10.331%	$33.5958	$33.60	$33.60	$33.60
Purchase #4	$178.65	12.482%	$200.9491	$200.95	$200.95	$200.90
Purchase #5	$191.69	12.291%	$215.2506	$215.25	$215.25	$215.30
Purchase #6	$79.86	7.327%	$85.7113	$85.71	$85.70	$85.70
Purchase #7	$16.82	11.717%	$18.7908	$18.79	$18.80	$18.80
7 purchase totals =	$803.60		$882.5966	$882.60	$882.60	$882.60