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	$164.72	5.145%	$173.1948	$173.19	$173.20	$173.20
Purchase #2	$147.75	11.284%	$164.4221	$164.42	$164.40	$164.40
Purchase #3	$22.88	13.193%	$25.8986	$25.90	$25.90	$25.90
Purchase #4	$86.91	12.308%	$97.6069	$97.61	$97.60	$97.60
Purchase #5	$190.78	11.644%	$212.9944	$212.99	$213.00	$213.00
Purchase #6	$102.83	8.293%	$111.3577	$111.36	$111.35	$111.40
Purchase #7	$207.48	11.173%	$230.6617	$230.66	$230.65	$230.70
7 purchase totals =	$923.35		$1,016.1362	$1,016.13	$1,016.10	$1,016.20