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	$160.65	8.144%	$173.7333	$173.73	$173.75	$173.70
Purchase #2	$217.30	11.758%	$242.8501	$242.85	$242.85	$242.90
Purchase #3	$101.59	9.285%	$111.0226	$111.02	$111.00	$111.00
Purchase #4	$117.49	10.686%	$130.045	$130.05	$130.05	$130.00
Purchase #5	$54.58	9.858%	$59.9605	$59.96	$59.95	$60.00
Purchase #6	$142.94	6.440%	$152.1453	$152.15	$152.15	$152.10
Purchase #7	$204.95	6.273%	$217.8065	$217.81	$217.80	$217.80
7 purchase totals =	$999.50		$1,087.5633	$1,087.57	$1,087.55	$1,087.50