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	$229.51	6.377%	$244.1459	$244.15	$244.15	$244.10
Purchase #2	$120.94	5.373%	$127.4381	$127.44	$127.45	$127.40
Purchase #3	$152.35	9.172%	$166.3235	$166.32	$166.30	$166.30
Purchase #4	$227.59	12.367%	$255.7361	$255.74	$255.75	$255.70
Purchase #5	$85.65	12.831%	$96.6398	$96.64	$96.65	$96.60
Purchase #6	$10.67	5.426%	$11.249	$11.25	$11.25	$11.20
Purchase #7	$14.32	8.843%	$15.5863	$15.59	$15.60	$15.60
7 purchase totals =	$841.03		$917.1187	$917.13	$917.15	$916.90