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	$184.97	13.169%	$209.3287	$209.33	$209.35	$209.30
Purchase #2	$11.71	3.137%	$12.0773	$12.08	$12.10	$12.10
Purchase #3	$40.94	10.739%	$45.3365	$45.34	$45.35	$45.30
Purchase #4	$133.38	13.321%	$151.1475	$151.15	$151.15	$151.10
Purchase #5	$173.33	13.186%	$196.1853	$196.19	$196.20	$196.20
Purchase #6	$29.32	8.431%	$31.792	$31.79	$31.80	$31.80
Purchase #7	$124.91	10.310%	$137.7882	$137.79	$137.80	$137.80
7 purchase totals =	$698.56		$783.6555	$783.67	$783.75	$783.60