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	$210.40	6.559%	$224.2001	$224.20	$224.20	$224.20
Purchase #2	$221.71	7.749%	$238.8903	$238.89	$238.90	$238.90
Purchase #3	$208.72	10.460%	$230.5521	$230.55	$230.55	$230.60
Purchase #4	$19.78	4.432%	$20.6566	$20.66	$20.65	$20.70
Purchase #5	$95.86	8.744%	$104.242	$104.24	$104.25	$104.20
Purchase #6	$21.31	3.577%	$22.0723	$22.07	$22.05	$22.10
Purchase #7	$238.64	13.637%	$271.1833	$271.18	$271.20	$271.20
7 purchase totals =	$1,016.42		$1,111.7967	$1,111.79	$1,111.80	$1,111.90