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	$246.64	13.577%	$280.1263	$280.13	$280.15	$280.10
Purchase #2	$213.72	3.629%	$221.4759	$221.48	$221.50	$221.50
Purchase #3	$17.67	9.647%	$19.3746	$19.37	$19.35	$19.40
Purchase #4	$131.43	6.304%	$139.7153	$139.72	$139.70	$139.70
Purchase #5	$145.78	4.479%	$152.3095	$152.31	$152.30	$152.30
Purchase #6	$18.36	6.239%	$19.5055	$19.51	$19.50	$19.50
Purchase #7	$12.52	8.533%	$13.5883	$13.59	$13.60	$13.60
7 purchase totals =	$786.12		$846.0954	$846.11	$846.10	$846.10