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	$101.45	3.553%	$105.0545	$105.05	$105.05	$105.10
Purchase #2	$135.42	7.674%	$145.8121	$145.81	$145.80	$145.80
Purchase #3	$215.71	12.441%	$242.5465	$242.55	$242.55	$242.50
Purchase #4	$118.35	3.151%	$122.0792	$122.08	$122.10	$122.10
Purchase #5	$181.51	4.810%	$190.2406	$190.24	$190.25	$190.20
Purchase #6	$215.85	4.487%	$225.5352	$225.54	$225.55	$225.50
Purchase #7	$46.90	12.531%	$52.777	$52.78	$52.80	$52.80
7 purchase totals =	$1,015.19		$1,084.0451	$1,084.05	$1,084.10	$1,084.00