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	$137.30	10.515%	$151.7371	$151.74	$151.75	$151.70
Purchase #2	$239.32	6.429%	$254.7059	$254.71	$254.70	$254.70
Purchase #3	$94.44	11.836%	$105.6179	$105.62	$105.60	$105.60
Purchase #4	$38.63	8.833%	$42.0422	$42.04	$42.05	$42.00
Purchase #5	$157.74	7.729%	$169.9317	$169.93	$169.95	$169.90
Purchase #6	$110.65	5.264%	$116.4746	$116.47	$116.45	$116.50
Purchase #7	$146.68	12.496%	$165.0091	$165.01	$165.00	$165.00
7 purchase totals =	$924.76		$1,005.5185	$1,005.52	$1,005.50	$1,005.40