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	$171.75	4.371%	$179.2572	$179.26	$179.25	$179.30
Purchase #2	$98.90	12.384%	$111.1478	$111.15	$111.15	$111.10
Purchase #3	$37.61	3.255%	$38.8342	$38.83	$38.85	$38.80
Purchase #4	$118.72	10.439%	$131.1132	$131.11	$131.10	$131.10
Purchase #5	$164.66	11.545%	$183.67	$183.67	$183.65	$183.70
Purchase #6	$56.32	9.660%	$61.7605	$61.76	$61.75	$61.80
Purchase #7	$175.76	3.547%	$181.9942	$181.99	$182.00	$182.00
7 purchase totals =	$823.72		$887.7771	$887.77	$887.75	$887.80