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	$33.25	5.718%	$35.1512	$35.15	$35.15	$35.20
Purchase #2	$212.94	4.271%	$222.0347	$222.03	$222.05	$222.00
Purchase #3	$90.98	9.202%	$99.352	$99.35	$99.35	$99.40
Purchase #4	$211.31	5.782%	$223.5279	$223.53	$223.55	$223.50
Purchase #5	$159.70	8.804%	$173.76	$173.76	$173.75	$173.80
Purchase #6	$246.67	7.864%	$266.0681	$266.07	$266.05	$266.10
Purchase #7	$97.32	6.278%	$103.4297	$103.43	$103.45	$103.40
7 purchase totals =	$1,052.17		$1,123.3236	$1,123.32	$1,123.35	$1,123.40