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	$118.67	9.765%	$130.2581	$130.26	$130.25	$130.30
Purchase #2	$52.52	6.719%	$56.0488	$56.05	$56.05	$56.00
Purchase #3	$245.41	13.814%	$279.3109	$279.31	$279.30	$279.30
Purchase #4	$199.31	11.192%	$221.6168	$221.62	$221.60	$221.60
Purchase #5	$94.79	9.201%	$103.5116	$103.51	$103.50	$103.50
Purchase #6	$49.71	5.521%	$52.4545	$52.45	$52.45	$52.50
Purchase #7	$223.31	4.415%	$233.1691	$233.17	$233.15	$233.20
7 purchase totals =	$983.72		$1,076.3698	$1,076.37	$1,076.30	$1,076.40