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	$212.75	4.473%	$222.2663	$222.27	$222.25	$222.30
Purchase #2	$102.74	8.104%	$111.066	$111.07	$111.05	$111.10
Purchase #3	$228.96	9.441%	$250.5761	$250.58	$250.60	$250.60
Purchase #4	$48.29	4.150%	$50.294	$50.29	$50.30	$50.30
Purchase #5	$89.89	4.584%	$94.0106	$94.01	$94.00	$94.00
Purchase #6	$158.55	11.634%	$176.9957	$177.00	$177.00	$177.00
Purchase #7	$97.89	12.203%	$109.8355	$109.84	$109.85	$109.80
7 purchase totals =	$939.07		$1,015.0442	$1,015.06	$1,015.05	$1,015.10