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	$50.43	10.260%	$55.6041	$55.60	$55.60	$55.60
Purchase #2	$37.33	3.838%	$38.7627	$38.76	$38.75	$38.80
Purchase #3	$173.94	12.124%	$195.0285	$195.03	$195.05	$195.00
Purchase #4	$10.76	7.249%	$11.54	$11.54	$11.55	$11.50
Purchase #5	$43.77	3.103%	$45.1282	$45.13	$45.15	$45.10
Purchase #6	$206.54	11.488%	$230.2673	$230.27	$230.25	$230.30
Purchase #7	$156.92	9.311%	$171.5308	$171.53	$171.55	$171.50
7 purchase totals =	$679.69		$747.8616	$747.86	$747.90	$747.80