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	$230.41	4.766%	$241.3913	$241.39	$241.40	$241.40
Purchase #2	$196.32	9.670%	$215.3041	$215.30	$215.30	$215.30
Purchase #3	$115.82	12.809%	$130.6554	$130.66	$130.65	$130.70
Purchase #4	$33.59	13.540%	$38.1381	$38.14	$38.15	$38.10
Purchase #5	$196.49	7.218%	$210.6726	$210.67	$210.65	$210.70
Purchase #6	$53.93	4.473%	$56.3423	$56.34	$56.35	$56.30
Purchase #7	$107.94	10.192%	$118.9412	$118.94	$118.95	$118.90
7 purchase totals =	$934.50		$1,011.4450	$1,011.44	$1,011.45	$1,011.40