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	$139.38	11.460%	$155.3529	$155.35	$155.35	$155.40
Purchase #2	$162.91	9.328%	$178.1062	$178.11	$178.10	$178.10
Purchase #3	$154.33	12.833%	$174.1352	$174.14	$174.15	$174.10
Purchase #4	$86.70	6.613%	$92.4335	$92.43	$92.45	$92.40
Purchase #5	$39.59	6.318%	$42.0913	$42.09	$42.10	$42.10
Purchase #6	$136.86	4.182%	$142.5835	$142.58	$142.60	$142.60
Purchase #7	$204.41	7.754%	$220.26	$220.26	$220.25	$220.30
7 purchase totals =	$924.18		$1,004.9626	$1,004.96	$1,005.00	$1,005.00