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	$206.41	11.711%	$230.5827	$230.58	$230.60	$230.60
Purchase #2	$240.63	3.830%	$249.8461	$249.85	$249.85	$249.80
Purchase #3	$135.83	6.812%	$145.0827	$145.08	$145.10	$145.10
Purchase #4	$175.56	9.244%	$191.7888	$191.79	$191.80	$191.80
Purchase #5	$187.52	3.175%	$193.4738	$193.47	$193.45	$193.50
Purchase #6	$16.82	8.409%	$18.2344	$18.23	$18.25	$18.20
Purchase #7	$78.88	4.318%	$82.286	$82.29	$82.30	$82.30
7 purchase totals =	$1,041.65		$1,111.2945	$1,111.29	$1,111.35	$1,111.30