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	$141.29	4.395%	$147.4997	$147.50	$147.50	$147.50
Purchase #2	$226.54	5.104%	$238.1026	$238.10	$238.10	$238.10
Purchase #3	$45.90	7.106%	$49.1617	$49.16	$49.15	$49.20
Purchase #4	$100.93	4.525%	$105.4971	$105.50	$105.50	$105.50
Purchase #5	$249.37	3.476%	$258.0381	$258.04	$258.05	$258.00
Purchase #6	$100.50	11.868%	$112.4273	$112.43	$112.45	$112.40
Purchase #7	$240.92	9.724%	$264.3471	$264.35	$264.35	$264.30
7 purchase totals =	$1,105.45		$1,175.0736	$1,175.08	$1,175.10	$1,175.00