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	$143.26	10.559%	$158.3868	$158.39	$158.40	$158.40
Purchase #2	$208.91	3.318%	$215.8416	$215.84	$215.85	$215.80
Purchase #3	$158.29	5.480%	$166.9643	$166.96	$166.95	$167.00
Purchase #4	$187.88	13.169%	$212.6219	$212.62	$212.60	$212.60
Purchase #5	$161.39	4.458%	$168.5848	$168.58	$168.60	$168.60
Purchase #6	$233.94	13.232%	$264.8949	$264.89	$264.90	$264.90
Purchase #7	$53.55	11.374%	$59.6408	$59.64	$59.65	$59.60
7 purchase totals =	$1,147.22		$1,246.9351	$1,246.92	$1,246.95	$1,246.90