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	$106.84	5.595%	$112.8177	$112.82	$112.80	$112.80
Purchase #2	$97.75	4.668%	$102.313	$102.31	$102.30	$102.30
Purchase #3	$104.44	5.111%	$109.7779	$109.78	$109.80	$109.80
Purchase #4	$59.90	9.288%	$65.4635	$65.46	$65.45	$65.50
Purchase #5	$164.45	5.286%	$173.1428	$173.14	$173.15	$173.10
Purchase #6	$75.58	3.309%	$78.0809	$78.08	$78.10	$78.10
Purchase #7	$112.36	10.194%	$123.814	$123.81	$123.80	$123.80
7 purchase totals =	$721.32		$765.4098	$765.40	$765.40	$765.40