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	$178.78	11.853%	$199.9708	$199.97	$199.95	$200.00
Purchase #2	$81.57	9.747%	$89.5206	$89.52	$89.50	$89.50
Purchase #3	$15.75	11.180%	$17.5109	$17.51	$17.50	$17.50
Purchase #4	$50.64	4.677%	$53.0084	$53.01	$53.00	$53.00
Purchase #5	$230.51	4.745%	$241.4477	$241.45	$241.45	$241.40
Purchase #6	$79.31	6.621%	$84.5611	$84.56	$84.55	$84.60
Purchase #7	$64.40	11.850%	$72.0314	$72.03	$72.05	$72.00
7 purchase totals =	$700.96		$758.0509	$758.05	$758.00	$758.00