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	$123.36	9.170%	$134.6721	$134.67	$134.65	$134.70
Purchase #2	$120.78	13.201%	$136.7242	$136.72	$136.70	$136.70
Purchase #3	$95.26	9.809%	$104.6041	$104.60	$104.60	$104.60
Purchase #4	$203.87	4.171%	$212.3734	$212.37	$212.35	$212.40
Purchase #5	$237.55	12.859%	$268.0966	$268.10	$268.10	$268.10
Purchase #6	$132.94	11.564%	$148.3132	$148.31	$148.30	$148.30
Purchase #7	$88.67	13.735%	$100.8488	$100.85	$100.85	$100.80
7 purchase totals =	$1,002.43		$1,105.6324	$1,105.62	$1,105.55	$1,105.60