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	$211.77	12.838%	$238.957	$238.96	$238.95	$239.00
Purchase #2	$230.96	13.470%	$262.0703	$262.07	$262.05	$262.10
Purchase #3	$149.64	4.441%	$156.2855	$156.29	$156.30	$156.30
Purchase #4	$128.99	13.522%	$146.432	$146.43	$146.45	$146.40
Purchase #5	$155.92	5.753%	$164.8901	$164.89	$164.90	$164.90
Purchase #6	$115.91	3.194%	$119.6122	$119.61	$119.60	$119.60
Purchase #7	$89.31	7.871%	$96.3396	$96.34	$96.35	$96.30
7 purchase totals =	$1,082.50		$1,184.5867	$1,184.59	$1,184.60	$1,184.60