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	$217.44	11.130%	$241.6411	$241.64	$241.65	$241.60
Purchase #2	$73.74	10.266%	$81.3101	$81.31	$81.30	$81.30
Purchase #3	$182.96	4.289%	$190.8072	$190.81	$190.80	$190.80
Purchase #4	$38.91	4.162%	$40.5294	$40.53	$40.55	$40.50
Purchase #5	$28.94	9.817%	$31.781	$31.78	$31.80	$31.80
Purchase #6	$61.27	7.521%	$65.8781	$65.88	$65.90	$65.90
Purchase #7	$63.43	5.856%	$67.1445	$67.14	$67.15	$67.10
7 purchase totals =	$666.69		$719.0914	$719.09	$719.15	$719.00