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	$70.93	3.496%	$73.4097	$73.41	$73.40	$73.40
Purchase #2	$214.60	12.392%	$241.1932	$241.19	$241.20	$241.20
Purchase #3	$83.88	7.231%	$89.9454	$89.95	$89.95	$89.90
Purchase #4	$98.34	12.857%	$110.9836	$110.98	$111.00	$111.00
Purchase #5	$10.81	7.238%	$11.5924	$11.59	$11.60	$11.60
Purchase #6	$144.30	12.823%	$162.8036	$162.80	$162.80	$162.80
Purchase #7	$250.51	5.422%	$264.0927	$264.09	$264.10	$264.10
7 purchase totals =	$873.37		$954.0206	$954.01	$954.05	$954.00