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	$23.50	3.187%	$24.2489	$24.25	$24.25	$24.20
Purchase #2	$127.92	13.763%	$145.5256	$145.53	$145.55	$145.50
Purchase #3	$65.98	7.843%	$71.1548	$71.15	$71.15	$71.20
Purchase #4	$238.33	10.698%	$263.8265	$263.83	$263.85	$263.80
Purchase #5	$190.42	7.688%	$205.0595	$205.06	$205.05	$205.10
Purchase #6	$205.50	8.742%	$223.4648	$223.46	$223.45	$223.50
Purchase #7	$96.30	7.343%	$103.3713	$103.37	$103.35	$103.40
7 purchase totals =	$947.95		$1,036.6514	$1,036.65	$1,036.65	$1,036.70