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	$102.30	9.218%	$111.73	$111.73	$111.75	$111.70
Purchase #2	$150.65	9.159%	$164.448	$164.45	$164.45	$164.40
Purchase #3	$145.33	10.775%	$160.9893	$160.99	$161.00	$161.00
Purchase #4	$111.96	7.405%	$120.2506	$120.25	$120.25	$120.30
Purchase #5	$38.74	9.444%	$42.3986	$42.40	$42.40	$42.40
Purchase #6	$51.39	3.185%	$53.0268	$53.03	$53.05	$53.00
Purchase #7	$159.46	8.629%	$173.2198	$173.22	$173.20	$173.20
7 purchase totals =	$759.83		$826.0631	$826.07	$826.10	$826.00