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	$94.99	4.523%	$99.2864	$99.29	$99.30	$99.30
Purchase #2	$222.74	3.608%	$230.7765	$230.78	$230.80	$230.80
Purchase #3	$233.46	5.504%	$246.3096	$246.31	$246.30	$246.30
Purchase #4	$141.71	13.229%	$160.4568	$160.46	$160.45	$160.50
Purchase #5	$19.78	8.518%	$21.4649	$21.46	$21.45	$21.50
Purchase #6	$107.71	8.751%	$117.1357	$117.14	$117.15	$117.10
Purchase #7	$102.86	6.381%	$109.4235	$109.42	$109.40	$109.40
7 purchase totals =	$923.25		$984.8534	$984.86	$984.85	$984.90