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	$112.59	9.856%	$123.6869	$123.69	$123.70	$123.70
Purchase #2	$97.94	8.682%	$106.4432	$106.44	$106.45	$106.40
Purchase #3	$100.54	11.123%	$111.7231	$111.72	$111.70	$111.70
Purchase #4	$188.55	12.852%	$212.7824	$212.78	$212.80	$212.80
Purchase #5	$162.75	5.389%	$171.5206	$171.52	$171.50	$171.50
Purchase #6	$223.50	8.375%	$242.2181	$242.22	$242.20	$242.20
Purchase #7	$95.93	4.238%	$99.9955	$100.00	$100.00	$100.00
7 purchase totals =	$981.80		$1,068.3698	$1,068.37	$1,068.35	$1,068.30