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	$101.30	4.499%	$105.8575	$105.86	$105.85	$105.90
Purchase #2	$248.36	9.643%	$272.3094	$272.31	$272.30	$272.30
Purchase #3	$52.86	6.485%	$56.288	$56.29	$56.30	$56.30
Purchase #4	$82.37	3.313%	$85.0989	$85.10	$85.10	$85.10
Purchase #5	$46.88	5.492%	$49.4546	$49.45	$49.45	$49.50
Purchase #6	$141.64	13.617%	$160.9271	$160.93	$160.95	$160.90
Purchase #7	$49.70	7.378%	$53.3669	$53.37	$53.35	$53.40
7 purchase totals =	$723.11		$783.3024	$783.31	$783.30	$783.40