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	$217.91	12.248%	$244.5996	$244.60	$244.60	$244.60
Purchase #2	$157.65	10.724%	$174.5564	$174.56	$174.55	$174.60
Purchase #3	$132.50	10.150%	$145.9488	$145.95	$145.95	$145.90
Purchase #4	$42.29	3.170%	$43.6306	$43.63	$43.65	$43.60
Purchase #5	$168.94	11.143%	$187.765	$187.77	$187.75	$187.80
Purchase #6	$197.94	6.401%	$210.6101	$210.61	$210.60	$210.60
Purchase #7	$170.57	4.810%	$178.7744	$178.77	$178.75	$178.80
7 purchase totals =	$1,087.80		$1,185.8849	$1,185.89	$1,185.85	$1,185.90