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	$109.98	7.718%	$118.4683	$118.47	$118.45	$118.50
Purchase #2	$47.86	3.737%	$49.6485	$49.65	$49.65	$49.60
Purchase #3	$94.41	4.171%	$98.3478	$98.35	$98.35	$98.30
Purchase #4	$81.51	10.127%	$89.7645	$89.76	$89.75	$89.80
Purchase #5	$97.72	8.415%	$105.9431	$105.94	$105.95	$105.90
Purchase #6	$218.54	6.226%	$232.1463	$232.15	$232.15	$232.10
Purchase #7	$82.56	11.826%	$92.3235	$92.32	$92.30	$92.30
7 purchase totals =	$732.58		$786.6420	$786.64	$786.60	$786.50