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	$220.33	4.495%	$230.2338	$230.23	$230.25	$230.20
Purchase #2	$39.89	13.870%	$45.4227	$45.42	$45.40	$45.40
Purchase #3	$178.68	5.311%	$188.1697	$188.17	$188.15	$188.20
Purchase #4	$183.71	3.570%	$190.2684	$190.27	$190.25	$190.30
Purchase #5	$151.32	7.289%	$162.3497	$162.35	$162.35	$162.30
Purchase #6	$97.74	3.706%	$101.3622	$101.36	$101.35	$101.40
Purchase #7	$196.71	4.680%	$205.916	$205.92	$205.90	$205.90
7 purchase totals =	$1,068.38		$1,123.7225	$1,123.72	$1,123.65	$1,123.70