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	$63.86	11.632%	$71.2882	$71.29	$71.30	$71.30
Purchase #2	$165.76	5.174%	$174.3364	$174.34	$174.35	$174.30
Purchase #3	$6.85	3.398%	$7.0828	$7.08	$7.10	$7.10
Purchase #4	$51.89	13.466%	$58.8775	$58.88	$58.90	$58.90
Purchase #5	$98.47	12.858%	$111.1313	$111.13	$111.15	$111.10
Purchase #6	$233.86	10.342%	$258.0458	$258.05	$258.05	$258.00
Purchase #7	$220.96	4.258%	$230.3685	$230.37	$230.35	$230.40
7 purchase totals =	$841.65		$911.1305	$911.14	$911.20	$911.10