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	$241.65	5.578%	$255.1292	$255.13	$255.15	$255.10
Purchase #2	$137.54	12.168%	$154.2759	$154.28	$154.30	$154.30
Purchase #3	$109.41	6.276%	$116.2766	$116.28	$116.30	$116.30
Purchase #4	$134.96	11.625%	$150.6491	$150.65	$150.65	$150.60
Purchase #5	$215.91	8.323%	$233.8802	$233.88	$233.90	$233.90
Purchase #6	$59.93	12.422%	$67.3745	$67.37	$67.35	$67.40
Purchase #7	$114.49	8.247%	$123.932	$123.93	$123.95	$123.90
7 purchase totals =	$1,013.89		$1,101.5175	$1,101.52	$1,101.60	$1,101.50