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	$59.95	8.779%	$65.213	$65.21	$65.20	$65.20
Purchase #2	$207.82	9.158%	$226.8522	$226.85	$226.85	$226.90
Purchase #3	$204.80	12.690%	$230.7891	$230.79	$230.80	$230.80
Purchase #4	$105.53	5.871%	$111.7257	$111.73	$111.75	$111.70
Purchase #5	$137.31	6.731%	$146.5523	$146.55	$146.55	$146.60
Purchase #6	$110.54	6.573%	$117.8058	$117.81	$117.80	$117.80
Purchase #7	$185.57	7.797%	$200.0389	$200.04	$200.05	$200.00
7 purchase totals =	$1,011.52		$1,098.9770	$1,098.98	$1,099.00	$1,099.00