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	$168.50	6.570%	$179.5705	$179.57	$179.55	$179.60
Purchase #2	$126.72	3.684%	$131.3884	$131.39	$131.40	$131.40
Purchase #3	$8.27	10.396%	$9.1297	$9.13	$9.15	$9.10
Purchase #4	$70.35	11.677%	$78.5648	$78.56	$78.55	$78.60
Purchase #5	$39.44	5.103%	$41.4526	$41.45	$41.45	$41.50
Purchase #6	$183.95	3.626%	$190.62	$190.62	$190.60	$190.60
Purchase #7	$245.76	10.351%	$271.1986	$271.20	$271.20	$271.20
7 purchase totals =	$842.99		$901.9246	$901.92	$901.90	$902.00