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	$102.96	8.296%	$111.5016	$111.50	$111.50	$111.50
Purchase #2	$10.41	12.393%	$11.7001	$11.70	$11.70	$11.70
Purchase #3	$198.72	6.567%	$211.7699	$211.77	$211.75	$211.80
Purchase #4	$213.41	13.651%	$242.5426	$242.54	$242.55	$242.50
Purchase #5	$237.49	6.514%	$252.9601	$252.96	$252.95	$253.00
Purchase #6	$158.83	12.238%	$178.2676	$178.27	$178.25	$178.30
Purchase #7	$90.78	12.428%	$102.0621	$102.06	$102.05	$102.10
7 purchase totals =	$1,012.60		$1,110.8040	$1,110.80	$1,110.75	$1,110.90