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	$74.42	11.112%	$82.6896	$82.69	$82.70	$82.70
Purchase #2	$134.38	4.400%	$140.2927	$140.29	$140.30	$140.30
Purchase #3	$109.81	12.435%	$123.4649	$123.46	$123.45	$123.50
Purchase #4	$104.56	13.470%	$118.6442	$118.64	$118.65	$118.60
Purchase #5	$135.68	7.612%	$146.008	$146.01	$146.00	$146.00
Purchase #6	$138.28	5.640%	$146.079	$146.08	$146.10	$146.10
Purchase #7	$170.78	4.548%	$178.5471	$178.55	$178.55	$178.50
7 purchase totals =	$867.91		$935.7255	$935.72	$935.75	$935.70