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	$65.96	4.796%	$69.1234	$69.12	$69.10	$69.10
Purchase #2	$206.61	8.302%	$223.7628	$223.76	$223.75	$223.80
Purchase #3	$67.33	4.859%	$70.6016	$70.60	$70.60	$70.60
Purchase #4	$67.80	7.561%	$72.9264	$72.93	$72.95	$72.90
Purchase #5	$99.67	3.469%	$103.1276	$103.13	$103.15	$103.10
Purchase #6	$34.30	13.429%	$38.9061	$38.91	$38.90	$38.90
Purchase #7	$134.76	4.724%	$141.1261	$141.13	$141.15	$141.10
7 purchase totals =	$676.43		$719.5740	$719.58	$719.60	$719.50