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	$68.57	5.203%	$72.1377	$72.14	$72.15	$72.10
Purchase #2	$136.84	3.817%	$142.0632	$142.06	$142.05	$142.10
Purchase #3	$30.26	4.173%	$31.5227	$31.52	$31.50	$31.50
Purchase #4	$227.78	9.826%	$250.1617	$250.16	$250.15	$250.20
Purchase #5	$21.31	6.230%	$22.6376	$22.64	$22.65	$22.60
Purchase #6	$158.75	8.403%	$172.0898	$172.09	$172.10	$172.10
Purchase #7	$168.39	10.799%	$186.5744	$186.57	$186.55	$186.60
7 purchase totals =	$811.90		$877.1871	$877.18	$877.15	$877.20