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	$105.88	11.172%	$117.7089	$117.71	$117.70	$117.70
Purchase #2	$102.90	8.700%	$111.8523	$111.85	$111.85	$111.90
Purchase #3	$150.68	5.373%	$158.776	$158.78	$158.80	$158.80
Purchase #4	$164.74	4.658%	$172.4136	$172.41	$172.40	$172.40
Purchase #5	$157.32	5.691%	$166.2731	$166.27	$166.25	$166.30
Purchase #6	$239.42	12.822%	$270.1184	$270.12	$270.10	$270.10
Purchase #7	$160.35	7.460%	$172.3121	$172.31	$172.30	$172.30
7 purchase totals =	$1,081.29		$1,169.4544	$1,169.45	$1,169.40	$1,169.50