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	$79.40	12.779%	$89.5465	$89.55	$89.55	$89.50
Purchase #2	$105.98	10.442%	$117.0464	$117.05	$117.05	$117.00
Purchase #3	$232.57	9.670%	$255.0595	$255.06	$255.05	$255.10
Purchase #4	$142.49	8.594%	$154.7356	$154.74	$154.75	$154.70
Purchase #5	$97.74	12.150%	$109.6154	$109.62	$109.60	$109.60
Purchase #6	$102.51	3.392%	$105.9871	$105.99	$106.00	$106.00
Purchase #7	$172.66	10.275%	$190.4008	$190.40	$190.40	$190.40
7 purchase totals =	$933.35		$1,022.3913	$1,022.41	$1,022.40	$1,022.30