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	$44.47	10.103%	$48.9628	$48.96	$48.95	$49.00
Purchase #2	$41.27	3.646%	$42.7747	$42.77	$42.75	$42.80
Purchase #3	$10.82	10.110%	$11.9139	$11.91	$11.90	$11.90
Purchase #4	$154.25	7.731%	$166.1751	$166.18	$166.20	$166.20
Purchase #5	$85.75	7.393%	$92.0895	$92.09	$92.10	$92.10
Purchase #6	$136.53	4.217%	$142.2875	$142.29	$142.30	$142.30
Purchase #7	$47.96	13.751%	$54.555	$54.56	$54.55	$54.60
7 purchase totals =	$521.05		$558.7585	$558.76	$558.75	$558.90