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	$65.73	9.234%	$71.7995	$71.80	$71.80	$71.80
Purchase #2	$63.85	13.839%	$72.6862	$72.69	$72.70	$72.70
Purchase #3	$102.96	7.862%	$111.0547	$111.05	$111.05	$111.10
Purchase #4	$210.69	7.493%	$226.477	$226.48	$226.50	$226.50
Purchase #5	$225.46	13.512%	$255.9242	$255.92	$255.90	$255.90
Purchase #6	$157.52	3.395%	$162.8678	$162.87	$162.85	$162.90
Purchase #7	$77.64	8.248%	$84.0437	$84.04	$84.05	$84.00
7 purchase totals =	$903.85		$984.8531	$984.85	$984.85	$984.90