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	$166.62	11.285%	$185.4231	$185.42	$185.40	$185.40
Purchase #2	$57.74	11.310%	$64.2704	$64.27	$64.25	$64.30
Purchase #3	$39.84	7.142%	$42.6854	$42.69	$42.70	$42.70
Purchase #4	$76.32	8.204%	$82.5813	$82.58	$82.60	$82.60
Purchase #5	$79.95	6.123%	$84.8453	$84.85	$84.85	$84.80
Purchase #6	$125.53	4.656%	$131.3747	$131.37	$131.35	$131.40
Purchase #7	$92.93	11.720%	$103.8214	$103.82	$103.80	$103.80
7 purchase totals =	$638.93		$695.0016	$695.00	$694.95	$695.00