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	$48.52	11.595%	$54.1459	$54.15	$54.15	$54.10
Purchase #2	$189.69	13.480%	$215.2602	$215.26	$215.25	$215.30
Purchase #3	$210.78	8.320%	$228.3169	$228.32	$228.30	$228.30
Purchase #4	$102.69	8.720%	$111.6446	$111.64	$111.65	$111.60
Purchase #5	$153.40	12.304%	$172.2743	$172.27	$172.25	$172.30
Purchase #6	$96.81	5.608%	$102.2391	$102.24	$102.25	$102.20
Purchase #7	$156.90	11.363%	$174.7285	$174.73	$174.75	$174.70
7 purchase totals =	$958.79		$1,058.6095	$1,058.61	$1,058.60	$1,058.50