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	$52.26	11.145%	$58.0844	$58.08	$58.10	$58.10
Purchase #2	$62.60	7.445%	$67.2606	$67.26	$67.25	$67.30
Purchase #3	$85.55	3.152%	$88.2465	$88.25	$88.25	$88.20
Purchase #4	$11.28	13.672%	$12.8222	$12.82	$12.80	$12.80
Purchase #5	$111.45	11.618%	$124.3983	$124.40	$124.40	$124.40
Purchase #6	$117.33	12.357%	$131.8285	$131.83	$131.85	$131.80
Purchase #7	$207.60	10.508%	$229.4146	$229.41	$229.40	$229.40
7 purchase totals =	$648.07		$712.0551	$712.05	$712.05	$712.00