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	$129.74	11.719%	$144.9442	$144.94	$144.95	$144.90
Purchase #2	$19.31	6.521%	$20.5692	$20.57	$20.55	$20.60
Purchase #3	$98.66	12.836%	$111.324	$111.32	$111.30	$111.30
Purchase #4	$92.48	12.289%	$103.8449	$103.84	$103.85	$103.80
Purchase #5	$224.84	5.456%	$237.1073	$237.11	$237.10	$237.10
Purchase #6	$183.32	9.637%	$200.9865	$200.99	$201.00	$201.00
Purchase #7	$145.78	4.163%	$151.8488	$151.85	$151.85	$151.80
7 purchase totals =	$894.13		$970.6249	$970.62	$970.60	$970.50